diff options
35 files changed, 1490 insertions, 1324 deletions
diff --git a/.gitignore b/.gitignore index 12cbc32f5..6375f2bc5 100644 --- a/.gitignore +++ b/.gitignore @@ -161,3 +161,5 @@ INSTALL /test-suite/standalone/test-scm-to-latin1-string /test-suite/standalone/test-scm-c-bind-keyword-arguments /libguile/vm-operations.h +/test-suite/standalone/test-foreign-object-c +/test-suite/standalone/test-srfi-4 diff --git a/doc/Makefile.am b/doc/Makefile.am index c2960453f..f1c694551 100644 --- a/doc/Makefile.am +++ b/doc/Makefile.am @@ -1,6 +1,6 @@ ## Process this file with Automake to create Makefile.in ## -## Copyright (C) 1998, 2002, 2006, 2008, 2009, 2010 Free Software Foundation, Inc. +## Copyright (C) 1998, 2002, 2006, 2008, 2009, 2010, 2014 Free Software Foundation, Inc. ## ## This file is part of GUILE. ## @@ -25,18 +25,6 @@ SUBDIRS = ref r5rs dist_man1_MANS = guile.1 -EXAMPLE_SMOB_FILES = \ - ChangeLog-2008 Makefile README image-type.c image-type.h myguile.c - -OLDFMT = oldfmt.c - -dist-hook: - cp $(srcdir)/$(OLDFMT) $(distdir)/ - mkdir $(distdir)/example-smob - for f in $(EXAMPLE_SMOB_FILES); do \ - cp $(srcdir)/example-smob/$$f $(distdir)/example-smob/; \ - done - EXTRA_DIST = groupings.alist ChangeLog-2008 # guile-api.alist include $(top_srcdir)/am/maintainer-dirs diff --git a/doc/README b/doc/README index 18862a6b8..75c1f7fd6 100644 --- a/doc/README +++ b/doc/README @@ -14,10 +14,6 @@ Please be aware that this is all very much work in progress (apart from the Revised^5 Report). Bug reports and contributions are welcome! -The file `oldfmt.c' contains a function which can be used by -application writers to support both old-style and new-style error -format strings. - The `sources' directory includes some stuff relevant to the Guile reference manual, and which may eventually be folded in to it. It's not immediately relevant, however, which is why it's not in this diff --git a/doc/example-smob/ChangeLog-2008 b/doc/example-smob/ChangeLog-2008 deleted file mode 100644 index 931860849..000000000 --- a/doc/example-smob/ChangeLog-2008 +++ /dev/null @@ -1,56 +0,0 @@ -2008-01-22 Neil Jerram <neil@ossau.uklinux.net> - - * COPYING: Removed. - -2004-09-24 Marius Vollmer <mvo@zagadka.de> - - * image-type.c: Updated from manual. - -2002-02-28 Marius Vollmer <mvo@zagadka.ping.de> - - * image-type.c (image_tag): Changed type to scm_t_bits. - (make_image): Use scm_gc_malloc instead of scm_must_malloc. - (free_image): Use scm_gc_free instead of free. Return zero. - -2001-05-30 Martin Grabmueller <mgrabmue@cs.tu-berlin.de> - - * image-type.c: Adapted to new typing and naming convention. - -2001-04-26 Neil Jerram <neil@ossau.uklinux.net> - - * image-type.c (make_image): Don't need to use SCM_NIMP before - SCM_STRINGP. - (clear_image): Use SCM_SMOB_PREDICATE. - (clear_image, mark_image, free_image, print_image): Use - SCM_SMOB_DATA rather than SCM_CDR. - -2000-06-20 Mikael Djurfeldt <mdj@thalamus.nada.kth.se> - - * image-type.c: Removed unused scm_smobfuns structure. - (init_image_type): Use standard smob type interface. - -Fri Jun 25 22:21:04 1999 Greg Badros <gjb@cs.washington.edu> - - * image-type.c: Updated example to use scm_make_smob_type_mfpe, - SCM_RETURN_NEWSMOB, SCM_NEWSMOB function and macros. - -1998-10-19 Jim Blandy <jimb@zwingli.cygnus.com> - - * image-type.c, myguile.c: Terminate copyright comments. - - * COPYING: New file. - * image-type.c myguile.c: Add copyright notice. - -1998-10-16 Jim Blandy <jimb@zwingli.cygnus.com> - - * Makefile (myguile): Fix link command, to put the Guile libraries - after the object files. The old command worked on my machine, but - I don't see how. - -1998-10-15 Jim Blandy <jimb@zwingli.cygnus.com> - - Created this directory for the Guile 1.3 release. Thanks to Jay - Glascoe for suggesting that we provide a complete, buildable - example! - * ChangeLog, Makefile, README, image-type.c, image-type.h, - myguile: New files. diff --git a/doc/example-smob/Makefile b/doc/example-smob/Makefile deleted file mode 100644 index d368d7b21..000000000 --- a/doc/example-smob/Makefile +++ /dev/null @@ -1,12 +0,0 @@ -CFLAGS = `pkg-config guile-2.2 --cflags` -LIBS = `pkg-config guile-2.2 --libs` - -O_FILES = image-type.o myguile.o - -all: myguile - -myguile: $(O_FILES) - $(CC) $(O_FILES) $(LIBS) -o myguile - -clean: - -rm -rf myguile $(O_FILES) diff --git a/doc/example-smob/README b/doc/example-smob/README deleted file mode 100644 index 1380db123..000000000 --- a/doc/example-smob/README +++ /dev/null @@ -1,6 +0,0 @@ -This is the example code for the ``Defining New Types (Smobs)'' -chapter of the Guile manual. - -When you try to execute the code, if the system complains that it -can't find libguile.so, you need to add the directory containing the -installed Guile libraries to your LD_LIBRARY_PATH environment variable. diff --git a/doc/example-smob/image-type.c b/doc/example-smob/image-type.c deleted file mode 100644 index fc28a7de1..000000000 --- a/doc/example-smob/image-type.c +++ /dev/null @@ -1,115 +0,0 @@ -/* image-type.c - * - * Copyright (C) 1998, 2000, 2004, 2006, 2011 Free Software Foundation, Inc. - * - * This program is free software; you can redistribute it and/or - * modify it under the terms of the GNU Lesser General Public License - * as published by the Free Software Foundation; either version 3, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, but - * WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU - * Lesser General Public License for more details. - * - * You should have received a copy of the GNU Lesser General Public - * License along with this software; see the file COPYING.LESSER. If - * not, write to the Free Software Foundation, Inc., 51 Franklin - * Street, Fifth Floor, Boston, MA 02110-1301 USA - */ - -#include <stdlib.h> -#include <libguile.h> - -static scm_t_bits image_tag; - -struct image -{ - int width, height; - char *pixels; - - /* The name of this image */ - SCM name; - - /* A function to call when this image is - modified, e.g., to update the screen, - or SCM_BOOL_F if no action necessary */ - SCM update_func; -}; - -static SCM -make_image (SCM name, SCM s_width, SCM s_height) -{ - SCM smob; - struct image *image; - int width = scm_to_int (s_width); - int height = scm_to_int (s_height); - - /* Step 1: Allocate the memory block. - */ - image = (struct image *) scm_gc_malloc (sizeof (struct image), "image"); - - /* Step 2: Initialize it with straight code. - */ - image->width = width; - image->height = height; - image->pixels = NULL; - image->name = SCM_BOOL_F; - image->update_func = SCM_BOOL_F; - - /* Step 3: Create the smob. - */ - SCM_NEWSMOB (smob, image_tag, image); - - /* Step 4: Finish the initialization. - */ - image->name = name; - image->pixels = scm_gc_malloc_pointerless (width * height, "image pixels"); - - return smob; -} - -SCM -clear_image (SCM image_smob) -{ - int area; - struct image *image; - - scm_assert_smob_type (image_tag, image_smob); - - image = (struct image *) SCM_SMOB_DATA (image_smob); - area = image->width * image->height; - memset (image->pixels, 0, area); - - /* Invoke the image's update function. - */ - if (scm_is_true (image->update_func)) - scm_call_0 (image->update_func); - - scm_remember_upto_here_1 (image_smob); - - return SCM_UNSPECIFIED; -} - -static int -print_image (SCM image_smob, SCM port, scm_print_state *pstate) -{ - struct image *image = (struct image *) SCM_SMOB_DATA (image_smob); - - scm_puts ("#<image ", port); - scm_display (image->name, port); - scm_puts (">", port); - - /* non-zero means success */ - return 1; -} - -void -init_image_type (void) -{ - image_tag = scm_make_smob_type ("image", sizeof (struct image)); - scm_set_smob_print (image_tag, print_image); - - scm_c_define_gsubr ("clear-image", 1, 0, 0, clear_image); - scm_c_define_gsubr ("make-image", 3, 0, 0, make_image); -} diff --git a/doc/example-smob/image-type.h b/doc/example-smob/image-type.h deleted file mode 100644 index 38fcf74c4..000000000 --- a/doc/example-smob/image-type.h +++ /dev/null @@ -1,3 +0,0 @@ -/* file "image-type.h" */ - -void init_image_type (void); diff --git a/doc/example-smob/myguile.c b/doc/example-smob/myguile.c deleted file mode 100644 index 30200dd03..000000000 --- a/doc/example-smob/myguile.c +++ /dev/null @@ -1,37 +0,0 @@ -/* myguile.c - * - * Copyright (C) 1998, 2006 Free Software Foundation, Inc. - * - * This program is free software; you can redistribute it and/or - * modify it under the terms of the GNU Lesser General Public License - * as published by the Free Software Foundation; either version 3, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, but - * WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU - * Lesser General Public License for more details. - * - * You should have received a copy of the GNU Lesser General Public - * License along with this software; see the file COPYING.LESSER. If - * not, write to the Free Software Foundation, Inc., 51 Franklin - * Street, Fifth Floor, Boston, MA 02110-1301 USA - */ - -#include <libguile.h> -#include "image-type.h" - -static void -inner_main (void *closure, int argc, char **argv) -{ - /* module initializations would go here */ - init_image_type(); - scm_shell (argc, argv); -} - -int -main (int argc, char **argv) -{ - scm_boot_guile (argc, argv, inner_main, 0); - return 0; /* never reached */ -} diff --git a/doc/oldfmt.c b/doc/oldfmt.c deleted file mode 100644 index f60afeddd..000000000 --- a/doc/oldfmt.c +++ /dev/null @@ -1,194 +0,0 @@ -/* Copyright (C) 2000,2001, 2006, 2008 Free Software Foundation, Inc. - * - * This program is free software; you can redistribute it and/or - * modify it under the terms of the GNU Lesser General Public License - * as published by the Free Software Foundation; either version 3, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, but - * WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU - * Lesser General Public License for more details. - * - * You should have received a copy of the GNU Lesser General Public - * License along with this software; see the file COPYING.LESSER. If - * not, write to the Free Software Foundation, Inc., 51 Franklin - * Street, Fifth Floor, Boston, MA 02110-1301 USA - */ - - - -/* From NEWS: - * - * * New primitive: `simple-format', affects `scm-error', scm_display_error, & scm_error message strings - * - * (ice-9 boot) makes `format' an alias for `simple-format' until possibly - * extended by the more sophisticated version in (ice-9 format) - * - * (simple-format port message . args) - * Write MESSAGE to DESTINATION, defaulting to `current-output-port'. - * MESSAGE can contain ~A (was %s) and ~S (was %S) escapes. When printed, - * the escapes are replaced with corresponding members of ARGS: - * ~A formats using `display' and ~S formats using `write'. - * If DESTINATION is #t, then use the `current-output-port', - * if DESTINATION is #f, then return a string containing the formatted text. - * Does not add a trailing newline." - * - * The two C procedures: scm_display_error and scm_error, as well as the - * primitive `scm-error', now use scm_format to do their work. This means - * that the message strings of all code must be updated to use ~A where %s - * was used before, and ~S where %S was used before. - * - * During the period when there still are a lot of old Guiles out there, - * you might want to support both old and new versions of Guile. - * - * There are basically two methods to achieve this. Both methods use - * autoconf. Put - * - * AC_CHECK_FUNCS(scm_simple_format) - * - * in your configure.in. - * - * Method 1: Use the string concatenation features of ANSI C's - * preprocessor. - * - * In C: - * - * #ifdef HAVE_SCM_SIMPLE_FORMAT - * #define FMT_S "~S" - * #else - * #define FMT_S "%S" - * #endif - * - * Then represent each of your error messages using a preprocessor macro: - * - * #define E_SPIDER_ERROR "There's a spider in your " ## FMT_S ## "!!!" - * - * In Scheme: - * - * (define fmt-s (if (defined? 'simple-format) "~S" "%S")) - * (define make-message string-append) - * - * (define e-spider-error - * (make-message "There's a spider in your " fmt-s "!!!")) - * - * Method 2: Use the oldfmt function found in doc/oldfmt.c. - * - * In C: - * - * scm_misc_error ("picnic", scm_c_oldfmt0 ("There's a spider in your ~S!!!"), - * ...); - * - * In Scheme: - * - * (scm-error 'misc-error "picnic" (oldfmt "There's a spider in your ~S!!!") - * ...) - * - */ - -/* - * Take a format string FROM adhering to the new standard format (~A and ~S - * as placeholders) of length N and return a string which is adapted - * to the format used by the Guile interpreter which you are running. - * - * On successive calls with similar strings but different storage, the - * same string with same storage is returned. This is necessary since - * the existence of a garbage collector in the system may cause the same - * format string to be represented with different storage at different - * calls. - */ - -char * -scm_c_oldfmt (char *from, int n) -{ -#ifdef HAVE_SCM_SIMPLE_FORMAT - return from; -#else - static struct { int n; char *from; char *to; } *strings; - static int size = 0; - static int n_strings = 0; - char *to; - int i; - - for (i = 0; i < n_strings; ++i) - if (n == strings[i].n && strncmp (from, strings[i].from, n) == 0) - return strings[i].to; - - if (n_strings == size) - { - if (size == 0) - { - size = 10; - strings = scm_must_malloc (size * sizeof (*strings), s_oldfmt); - } - else - { - int oldsize = size; - size = 3 * oldsize / 2; - strings = scm_must_realloc (strings, - oldsize * sizeof (*strings), - size * sizeof (*strings), - s_oldfmt); - } - } - - strings[n_strings].n = n; - strings[n_strings].from = strncpy (scm_must_malloc (n, s_oldfmt), from, n); - to = strings[n_strings].to = scm_must_malloc (n + 1, s_oldfmt); - n_strings++; - - for (i = 0; i < n; ++i) - { - if (from[i] == '~' && ++i < n) - { - if (from[i] == 'A') - { - to[i - 1] = '%'; - to[i] = 's'; - } - else if (from[i] == 'S') - { - to[i - 1] = '%'; - to[i] = 'S'; - } - else - { - to[i - 1] = '~'; - to[i] = from[i]; - } - continue; - } - to[i] = from[i]; - } - to[i] = '\0'; - - return to; -#endif -} - -char * -scm_c_oldfmt0 (char *s) -{ -#ifdef HAVE_SCM_SIMPLE_FORMAT - return s; -#else - return scm_c_oldfmt (s, strlen (s)); -#endif -} - -SCM_PROC (s_oldfmt, "oldfmt", 1, 0, 0, scm_oldfmt); - -SCM -scm_oldfmt (SCM s) -{ -#ifdef HAVE_SCM_SIMPLE_FORMAT - return s; -#else - int n; - SCM_ASSERT (SCM_NIMP (s) && SCM_STRINGP (s), s, 1, s_oldfmt); - n = SCM_LENGTH (s); - return scm_return_first (scm_mem2string (scm_c_oldfmt (SCM_ROCHARS (s), n), - n), - s); -#endif -} diff --git a/doc/ref/Makefile.am b/doc/ref/Makefile.am index 75b1745fa..83c6e5ee0 100644 --- a/doc/ref/Makefile.am +++ b/doc/ref/Makefile.am @@ -1,7 +1,7 @@ ## Process this file with Automake to create Makefile.in ## ## Copyright (C) 1998, 2004, 2006, 2008, 2009, 2010, -## 2011, 2013 Free Software Foundation, Inc. +## 2011, 2013, 2014 Free Software Foundation, Inc. ## ## This file is part of GUILE. ## @@ -33,6 +33,7 @@ guile_TEXINFOS = preface.texi \ api-scm.texi \ api-snarf.texi \ api-smobs.texi \ + api-foreign-objects.texi \ scheme-ideas.texi \ api-data.texi \ api-procedures.texi \ @@ -83,7 +84,7 @@ guile_TEXINFOS = preface.texi \ compiler.texi \ fdl.texi \ libguile-concepts.texi \ - libguile-smobs.texi \ + libguile-foreign-objects.texi \ libguile-snarf.texi \ libguile-linking.texi \ libguile-extensions.texi \ diff --git a/doc/ref/api-control.texi b/doc/ref/api-control.texi index 026308cac..4253a206a 100644 --- a/doc/ref/api-control.texi +++ b/doc/ref/api-control.texi @@ -1,7 +1,7 @@ @c -*-texinfo-*- @c This is part of the GNU Guile Reference Manual. @c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004, 2009, 2010, -@c 2011, 2012, 2013 Free Software Foundation, Inc. +@c 2011, 2012, 2013, 2014 Free Software Foundation, Inc. @c See the file guile.texi for copying conditions. @node Control Mechanisms @@ -1187,13 +1187,13 @@ The @var{body_data} and @var{handler_data} parameters are passed to the respective calls so an application can communicate extra information to those functions. -If the data consists of an @code{SCM} object, care should be taken -that it isn't garbage collected while still required. If the -@code{SCM} is a local C variable, one way to protect it is to pass a -pointer to that variable as the data parameter, since the C compiler -will then know the value must be held on the stack. Another way is to -use @code{scm_remember_upto_here_1} (@pxref{Remembering During -Operations}). +If the data consists of an @code{SCM} object, care should be taken that +it isn't garbage collected while still required. If the @code{SCM} is a +local C variable, one way to protect it is to pass a pointer to that +variable as the data parameter, since the C compiler will then know the +value must be held on the stack. Another way is to use +@code{scm_remember_upto_here_1} (@pxref{Foreign Object Memory +Management}). @end deftypefn diff --git a/doc/ref/api-foreign-objects.texi b/doc/ref/api-foreign-objects.texi new file mode 100644 index 000000000..f27f9c154 --- /dev/null +++ b/doc/ref/api-foreign-objects.texi @@ -0,0 +1,125 @@ +@c -*-texinfo-*- +@c This is part of the GNU Guile Reference Manual. +@c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004, 2009, 2013, 2014 +@c Free Software Foundation, Inc. +@c See the file guile.texi for copying conditions. + +@node Foreign Objects +@section Foreign Objects + +@cindex foreign object + +This chapter contains reference information related to defining and +working with foreign objects. @xref{Defining New Foreign Object Types}, +for a tutorial-like introduction to foreign objects. + +@deftp {C Type} scm_t_struct_finalize +This function type returns @code{void} and takes one @code{SCM} +argument. +@end deftp + +@deftypefn {C Function} SCM scm_make_foreign_object_type (SCM name, SCM slots, scm_t_struct_finalize finalizer) +Create a fresh foreign object type. @var{name} is a symbol naming the +type. @var{slots} is a list of symbols, each one naming a field in the +foreign object type. @var{finalizer} indicates the finalizer, and may +be @code{NULL}. +@end deftypefn + +@cindex finalizer +@cindex finalization + +We recommend that finalizers be avoided if possible. @xref{Foreign +Object Memory Management}. Finalizers must be async-safe and +thread-safe. Again, @pxref{Foreign Object Memory Management}. If you +are embedding Guile in an application that is not thread-safe, and you +define foreign object types that need finalization, you might want to +disable automatic finalization, and arrange to call +@code{scm_manually_run_finalizers ()} yourself. + +@deftypefn {C Function} int scm_set_automatic_finalization_enabled (int enabled_p) +Enable or disable automatic finalization. By default, Guile arranges to +invoke object finalizers automatically, in a separate thread if +possible. Passing a zero value for @var{enabled_p} will disable +automatic finalization for Guile as a whole. If you disable automatic +finalization, you will have to call @code{scm_run_finalizers ()} +periodically. + +Unlike most other Guile functions, you can call +@code{scm_set_automatic_finalization_enabled} before Guile has been +initialized. + +Return the previous status of automatic finalization. +@end deftypefn + +@deftypefn {C Function} int scm_run_finalizers (void) +Invoke any pending finalizers. Returns the number of finalizers that +were invoked. This function should be called when automatic +finalization is disabled, though it may be called if it is enabled as +well. +@end deftypefn + +@deftypefn {C Function} void scm_assert_foreign_object_type (SCM type, SCM val) +When @var{val} is a foreign object of the given @var{type}, do nothing. +Otherwise, signal an error. +@end deftypefn + +@deftypefn {C Function} SCM scm_make_foreign_object_0 (SCM type) +@deftypefnx {C Function} SCM scm_make_foreign_object_1 (SCM type, void *val0) +@deftypefnx {C Function} SCM scm_make_foreign_object_2 (SCM type, void *val0, void *val1) +@deftypefnx {C Function} SCM scm_make_foreign_object_3 (SCM type, void *val0, void *val1, void *val2) +@deftypefnx {C Function} SCM scm_make_foreign_object_n (SCM type, size_t n, void *vals[]) +Make a new foreign object of the type with type @var{type} and +initialize the first @var{n} fields to the given values, as appropriate. + +The number of fields for objects of a given type is fixed when the type +is created. It is an error to give more initializers than there are +fields in the value. It is perfectly fine to give fewer initializers +than needed; this is convenient when some fields are of non-pointer +types, and would be easier to initialize with the setters described +below. +@end deftypefn + +@deftypefn {C Function} void* scm_foreign_object_ref (SCM obj, size_t n); +@deftypefnx {C Function} scm_t_bits scm_foreign_object_unsigned_ref (SCM obj, size_t n); +@deftypefnx {C Function} scm_t_signed_bits scm_foreign_object_signed_ref (SCM obj, size_t n); +Return the value of the @var{n}th field of the foreign object @var{obj}. +The backing store for the fields is as wide as a @code{scm_t_bits} +value, which is at least as wide as a pointer. The different variants +handle casting in a portable way. +@end deftypefn + +@deftypefn {C Function} void scm_foreign_object_set_x (SCM obj, size_t n, void *val); +@deftypefnx {C Function} void scm_foreign_object_unsigned_set_x (SCM obj, size_t n, scm_t_bits val); +@deftypefnx {C Function} void scm_foreign_object_signed_set_x (SCM obj, size_t n, scm_t_signed_bits val); +Set the value of the @var{n}th field of the foreign object @var{obj} to +@var{val}, after portably converting to a @code{scm_t_bits} value, if +needed. +@end deftypefn + +One can also access foreign objects from Scheme. @xref{Foreign Objects +and Scheme}, for some examples. + +@example +(use-modules (system foreign-object)) +@end example + +@deffn {Scheme Procedure} make-foreign-object-type name slots [#:finalizer=#f] +Make a new foreign object type. See the above documentation for +@code{scm_make_foreign_object_type}; these functions are exactly +equivalent, except for the way in which the finalizer gets attached to +instances (an internal detail). + +The resulting value is a GOOPS class. @xref{GOOPS}, for more on classes +in Guile. +@end deffn + +@deffn {Scheme Syntax} define-foreign-object-type name constructor (slot ...) [#:finalizer=#f] +A convenience macro to define a type, using +@code{make-foreign-object-type}, and bind it to @var{name}. A +constructor will be bound to @var{constructor}, and getters will be +bound to each of @var{slot...}. +@end deffn + +@c Local Variables: +@c TeX-master: "guile.texi" +@c End: diff --git a/doc/ref/api-memory.texi b/doc/ref/api-memory.texi index 01bfe81b2..0e37d16fc 100644 --- a/doc/ref/api-memory.texi +++ b/doc/ref/api-memory.texi @@ -112,15 +112,16 @@ functions for dynamic memory allocation that are integrated into the garbage collector and the error reporting system. Memory blocks that are associated with Scheme objects (for example a -smob) should be allocated with @code{scm_gc_malloc} or +foreign object) should be allocated with @code{scm_gc_malloc} or @code{scm_gc_malloc_pointerless}. These two functions will either return a valid pointer or signal an error. Memory blocks allocated this -way can be freed with @code{scm_gc_free}; however, this is not strictly -needed: memory allocated with @code{scm_gc_malloc} or -@code{scm_gc_malloc_pointerless} is automatically reclaimed when the -garbage collector no longer sees any live reference to it@footnote{In -Guile up to version 1.8, memory allocated with @code{scm_gc_malloc} -@emph{had} to be freed with @code{scm_gc_free}.}. +way may be released explicitly; however, this is not strictly needed, +and we recommend @emph{not} calling @code{scm_gc_free}. All memory +allocated with @code{scm_gc_malloc} or @code{scm_gc_malloc_pointerless} +is automatically reclaimed when the garbage collector no longer sees any +live reference to it@footnote{In Guile up to version 1.8, memory +allocated with @code{scm_gc_malloc} @emph{had} to be freed with +@code{scm_gc_free}.}. Memory allocated with @code{scm_gc_malloc} is scanned for live pointers. This means that if @code{scm_gc_malloc}-allocated memory contains a @@ -204,7 +205,9 @@ size of a reallocated memory block as well. See below for a motivation. @deftypefn {C Function} void scm_gc_free (void *@var{mem}, size_t @var{size}, const char *@var{what}) Explicitly free the memory block pointed to by @var{mem}, which was -previously allocated by one of the above @code{scm_gc} functions. +previously allocated by one of the above @code{scm_gc} functions. This +function is almost always unnecessary, except for codebases that still +need to compile on Guile 1.8. Note that you need to explicitly pass the @var{size} parameter. This is done since it should normally be easy to provide this parameter @@ -225,7 +228,7 @@ often (as appropriate). It is especially important to call this function when large unmanaged allocations, like images, may be freed by small Scheme allocations, like -SMOBs. +foreign objects. @end deftypefn diff --git a/doc/ref/api-smobs.texi b/doc/ref/api-smobs.texi index cfabd3988..f09474eef 100644 --- a/doc/ref/api-smobs.texi +++ b/doc/ref/api-smobs.texi @@ -9,9 +9,17 @@ @cindex smob -This chapter contains reference information related to defining and -working with smobs. See @ref{Defining New Types (Smobs)} for a -tutorial-like introduction to smobs. +A @dfn{smob} is a ``small object''. Before foreign objects were +introduced in Guile 2.0.12 (@pxref{Foreign Objects}), smobs were the +preferred way to for C code to define new kinds of Scheme objects. With +the exception of the so-called ``applicable SMOBs'' discussed below, +smobs are now a legacy interface and are headed for eventual +deprecation. @xref{Deprecation}. New code should use the foreign +object interface. + +This section contains reference information related to defining and +working with smobs. For a tutorial-like introduction to smobs, see +``Defining New Types (Smobs)'' in previous versions of this manual. @deftypefun scm_t_bits scm_make_smob_type (const char *name, size_t size) This function adds a new smob type, named @var{name}, with instance size @@ -26,9 +34,8 @@ deallocate the memory block pointed to by @code{SCM_SMOB_DATA} with @code{scm_gc_free} will be @var{name}. Default values are provided for the @emph{mark}, @emph{free}, -@emph{print}, and @emph{equalp} functions, as described in -@ref{Defining New Types (Smobs)}. If you want to customize any of -these functions, the call to @code{scm_make_smob_type} should be +@emph{print}, and @emph{equalp} functions. If you want to customize any +of these functions, the call to @code{scm_make_smob_type} should be immediately followed by calls to one or several of @code{scm_set_smob_mark}, @code{scm_set_smob_free}, @code{scm_set_smob_print}, and/or @code{scm_set_smob_equalp}. @@ -60,51 +67,30 @@ memory is automatically reclaimed by the garbage collector when it is no longer needed (@pxref{Memory Blocks, @code{scm_gc_malloc}}). @end deftypefn -Smob free functions must be thread-safe. @xref{Garbage Collecting -Smobs}, for a discussion on finalizers and concurrency. If you are +Smob free functions must be thread-safe. @xref{Foreign Object Memory +Management}, for a discussion on finalizers and concurrency. If you are embedding Guile in an application that is not thread-safe, and you define smob types that need finalization, you might want to disable automatic finalization, and arrange to call -@code{scm_manually_run_finalizers ()} yourself. - -@deftypefn {C Function} int scm_set_automatic_finalization_enabled (int enabled_p) -Enable or disable automatic finalization. By default, Guile arranges to -invoke object finalizers automatically, in a separate thread if -possible. Passing a zero value for @var{enabled_p} will disable -automatic finalization for Guile as a whole. If you disable automatic -finalization, you will have to call @code{scm_run_finalizers ()} -periodically. - -Unlike most other Guile functions, you can call -@code{scm_set_automatic_finalization_enabled} before Guile has been -initialized. - -Return the previous status of automatic finalization. -@end deftypefn - -@deftypefn {C Function} int scm_run_finalizers (void) -Invoke any pending finalizers. Returns the number of finalizers that -were invoked. This function should be called when automatic -finalization is disabled, though it may be called if it is enabled as -well. -@end deftypefn - - -@cindex precise marking +@code{scm_manually_run_finalizers ()} yourself. @xref{Foreign Objects}. @deftypefn {C Function} void scm_set_smob_mark (scm_t_bits tc, SCM (*mark) (SCM obj)) This function sets the smob marking procedure for the smob type specified by the tag @var{tc}. @var{tc} is the tag returned by @code{scm_make_smob_type}. -Defining a marking procedure may sometimes be unnecessary because large -parts of the process' memory (with the exception of -@code{scm_gc_malloc_pointerless} regions, and @code{malloc}- or -@code{scm_malloc}-allocated memory) are scanned for live -pointers@footnote{Conversely, in Guile up to the 1.8 series, the marking -procedure was always required. The reason is that Guile's GC would only -look for pointers in the memory area used for built-in types (the -@dfn{cell heap}), not in user-allocated or statically allocated memory. -This approach is often referred to as @dfn{precise marking}.}. +Defining a marking procedure is almost always the wrong thing to do. It +is much, much preferable to allocate smob data with the +@code{scm_gc_malloc} and @code{scm_gc_malloc_pointerless} functions, and +allow the GC to trace pointers automatically. + +Any mark procedures you see currently almost surely date from the time +of Guile 1.8, before the switch to the Boehm-Demers-Weiser collector. +Such smob implementations should be changed to just use +@code{scm_gc_malloc} and friends, and to lose their mark function. + +If you decide to keep the mark function, note that it may be called on +objects that are on the free list. Please read and digest the comments +from the BDW GC's @code{gc/gc_mark.h} header. The @var{mark} procedure must cause @code{scm_gc_mark} to be called for every @code{SCM} value that is directly referenced by the smob diff --git a/doc/ref/api-utility.texi b/doc/ref/api-utility.texi index 76c50b2ca..ffdf27687 100644 --- a/doc/ref/api-utility.texi +++ b/doc/ref/api-utility.texi @@ -1,6 +1,6 @@ @c -*-texinfo-*- @c This is part of the GNU Guile Reference Manual. -@c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004, 2011, 2012, 2013 +@c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004, 2011, 2012, 2013, 2014 @c Free Software Foundation, Inc. @c See the file guile.texi for copying conditions. @@ -163,12 +163,14 @@ same. into an infinite loop if asked to compare two circular lists or similar. -New application-defined object types (@pxref{Defining New Types -(Smobs)}) have an @code{equalp} handler which is called by -@code{equal?}. This lets an application traverse the contents or -control what is considered @code{equal?} for two objects of such a -type. If there's no such handler, the default is to just compare as -per @code{eq?}. +GOOPS object types (@pxref{GOOPS}), including foreign object types +(@pxref{Defining New Foreign Object Types}), can have an @code{equal?} +implementation specialized on two values of the same type. If +@code{equal?} is called on two GOOPS objects of the same type, +@code{equal?} will dispatch out to a generic function. This lets an +application traverse the contents or control what is considered +@code{equal?} for two objects of such a type. If there's no such +handler, the default is to just compare as per @code{eq?}. @end deffn diff --git a/doc/ref/guile.texi b/doc/ref/guile.texi index c43873cff..5f21188fa 100644 --- a/doc/ref/guile.texi +++ b/doc/ref/guile.texi @@ -246,7 +246,7 @@ continuations influence the control flow in a C program. This knowledge should make it straightforward to add new functions to Guile that can be called from Scheme. Adding new data types is also -possible and is done by defining @dfn{smobs}. +possible and is done by defining @dfn{foreign objects}. The @ref{Programming Overview} section of this part contains general musings and guidelines about programming with Guile. It explores @@ -267,7 +267,7 @@ etc. that make up Guile's application programming interface (API), * Linking Programs With Guile:: More precisely, with the libguile library. * Linking Guile with Libraries:: To extend Guile itself. * General Libguile Concepts:: General concepts for using libguile. -* Defining New Types (Smobs):: Adding new types to Guile. +* Defining New Foreign Object Types:: Adding new types to Guile. * Function Snarfing:: A way to define new functions. * Programming Overview:: An overview of Guile programming. * Autoconf Support:: Putting m4 to good use. @@ -277,7 +277,7 @@ etc. that make up Guile's application programming interface (API), @include libguile-linking.texi @include libguile-extensions.texi @include libguile-concepts.texi -@include libguile-smobs.texi +@include libguile-foreign-objects.texi @include libguile-snarf.texi @include libguile-program.texi @include libguile-autoconf.texi @@ -299,7 +299,8 @@ available through both Scheme and C interfaces. * Snarfing Macros:: Macros for snarfing initialization actions. * Simple Data Types:: Numbers, strings, booleans and so on. * Compound Data Types:: Data types for holding other data. -* Smobs:: Defining new data types in C. +* Foreign Objects:: Defining new data types in C. +* Smobs:: Use foreign objects instead. * Procedures:: Procedures. * Macros:: Extending the syntax of Scheme. * Utility Functions:: General utility functions. @@ -328,6 +329,7 @@ available through both Scheme and C interfaces. @include api-snarf.texi @include api-data.texi @include api-compound.texi +@include api-foreign-objects.texi @include api-smobs.texi @include api-procedures.texi @include api-macros.texi diff --git a/doc/ref/libguile-concepts.texi b/doc/ref/libguile-concepts.texi index 0103ad173..9e2eb7503 100644 --- a/doc/ref/libguile-concepts.texi +++ b/doc/ref/libguile-concepts.texi @@ -1,7 +1,7 @@ @c -*-texinfo-*- @c This is part of the GNU Guile Reference Manual. @c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004, 2005, 2010, -@c 2011, 2013 Free Software Foundation, Inc. +@c 2011, 2013, 2014 Free Software Foundation, Inc. @c See the file guile.texi for copying conditions. @node General Libguile Concepts @@ -191,38 +191,34 @@ periodically free all blocks that have been allocated but are not used by any active Scheme values. This activity is called @dfn{garbage collection}. -It is easy for Guile to remember all blocks of memory that it has -allocated for use by Scheme values, but you need to help it with finding -all Scheme values that are in use by C code. - -You do this when writing a SMOB mark function, for example -(@pxref{Garbage Collecting Smobs}). By calling this function, the -garbage collector learns about all references that your SMOB has to -other @code{SCM} values. - -Other references to @code{SCM} objects, such as global variables of type -@code{SCM} or other random data structures in the heap that contain -fields of type @code{SCM}, can be made visible to the garbage collector -by calling the functions @code{scm_gc_protect} or -@code{scm_permanent_object}. You normally use these functions for long -lived objects such as a hash table that is stored in a global variable. -For temporary references in local variables or function arguments, using -these functions would be too expensive. - -These references are handled differently: Local variables (and function -arguments) of type @code{SCM} are automatically visible to the garbage -collector. This works because the collector scans the stack for -potential references to @code{SCM} objects and considers all referenced -objects to be alive. The scanning considers each and every word of the -stack, regardless of what it is actually used for, and then decides -whether it could possibly be a reference to a @code{SCM} object. Thus, -the scanning is guaranteed to find all actual references, but it might -also find words that only accidentally look like references. These -`false positives' might keep @code{SCM} objects alive that would -otherwise be considered dead. While this might waste memory, keeping an -object around longer than it strictly needs to is harmless. This is why -this technique is called ``conservative garbage collection''. In -practice, the wasted memory seems to be no problem. +Guile's garbage collector will automatically discover references to +@code{SCM} objects that originate in global variables, static data +sections, function arguments or local variables on the C and Scheme +stacks, and values in machine registers. Other references to @code{SCM} +objects, such as those in other random data structures in the C heap +that contain fields of type @code{SCM}, can be made visible to the +garbage collector by calling the functions @code{scm_gc_protect} or +@code{scm_permanent_object}. Collectively, these values form the ``root +set'' of garbage collection; any value on the heap that is referenced +directly or indirectly by a member of the root set is preserved, and all +other objects are eligible for reclamation. + +The Scheme stack and heap are scanned precisely; that is to say, Guile +knows about all inter-object pointers on the Scheme stack and heap. +This is not the case, unfortunately, for pointers on the C stack and +static data segment. For this reason we have to scan the C stack and +static data segment @dfn{conservatively}; any value that looks like a +pointer to a GC-managed object is treated as such, whether it actually +is a reference or not. Thus, scanning the C stack and static data +segment is guaranteed to find all actual references, but it might also +find words that only accidentally look like references. These ``false +positives'' might keep @code{SCM} objects alive that would otherwise be +considered dead. While this might waste memory, keeping an object +around longer than it strictly needs to is harmless. This is why this +technique is called ``conservative garbage collection''. In practice, +the wasted memory seems to be no problem, as the static C root set is +almost always finite and small, given that the Scheme stack is separate +from the C stack. The stack of every thread is scanned in this way and the registers of the CPU and all other memory locations where local variables or function @@ -245,17 +241,17 @@ wanted. There are situations, however, where a @code{SCM} object needs to be around longer than its reference from a local variable or function parameter. This happens, for example, when you retrieve some pointer -from a smob and work with that pointer directly. The reference to the -@code{SCM} smob object might be dead after the pointer has been -retrieved, but the pointer itself (and the memory pointed to) is still -in use and thus the smob object must be protected. The compiler does -not know about this connection and might overwrite the @code{SCM} -reference too early. +from a foreign object and work with that pointer directly. The +reference to the @code{SCM} foreign object might be dead after the +pointer has been retrieved, but the pointer itself (and the memory +pointed to) is still in use and thus the foreign object must be +protected. The compiler does not know about this connection and might +overwrite the @code{SCM} reference too early. To get around this problem, you can use @code{scm_remember_upto_here_1} and its cousins. It will keep the compiler from overwriting the -reference. For a typical example of its use, see @ref{Remembering -During Operations}. +reference. @xref{Foreign Object Memory Management}. + @node Control Flow @subsection Control Flow diff --git a/doc/ref/libguile-foreign-objects.texi b/doc/ref/libguile-foreign-objects.texi new file mode 100644 index 000000000..11941d566 --- /dev/null +++ b/doc/ref/libguile-foreign-objects.texi @@ -0,0 +1,493 @@ +@c -*-texinfo-*- +@c This is part of the GNU Guile Reference Manual. +@c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004, 2005, 2010, 2011, 2013, 2014 +@c Free Software Foundation, Inc. +@c See the file guile.texi for copying conditions. + +@node Defining New Foreign Object Types +@section Defining New Foreign Object Types + +The @dfn{foreign object type} facility is Guile's mechanism for +importing object and types from C or other languages into Guile's +system. If you have a C @code{struct foo} type, for example, you can +define a corresponding Guile foreign object type that allows Scheme code +to handle @code{struct foo *} objects. + +To define a new foreign object type, the programmer provides Guile with +some essential information about the type --- what its name is, how many +fields it has, and its finalizer (if any) --- and Guile allocates a +fresh type for it. Foreign objects can be accessed from Scheme or from +C. + +@menu +* Defining Foreign Object Types:: +* Creating Foreign Objects:: +* Type Checking of Foreign Objects:: +* Foreign Object Memory Management:: +* Foreign Objects and Scheme:: +@end menu + +@node Defining Foreign Object Types +@subsection Defining Foreign Object Types + +To create a new foreign object type from C, call +@code{scm_make_foreign_object_type}. It returns a value of type +@code{SCM} which identifies the new type. + +Here is how one might declare a new type representing eight-bit +gray-scale images: + +@example +#include <libguile.h> + +struct image @{ + int width, height; + char *pixels; + + /* The name of this image */ + SCM name; + + /* A function to call when this image is + modified, e.g., to update the screen, + or SCM_BOOL_F if no action necessary */ + SCM update_func; +@}; + +static SCM image_type image_type; + +void +init_image_type (void) +@{ + SCM name, slots; + scm_t_struct_finalize finalizer; + + name = scm_from_utf8_symbol ("image"); + slots = scm_list_1 (scm_from_utf8_symbol ("data")); + finalizer = NULL; + + image_type = + scm_make_foreign_object_type (name, slots, finalizer); +@} +@end example + +The result is an initialized @code{image_type} value that identifies the +new foreign object type. The next section describes how to create +foreign objects and how to access their slots. + + +@node Creating Foreign Objects +@subsection Creating Foreign Objects + +Foreign objects contain zero or more ``slots'' of data. A slot can hold +a pointer, an integer that fits into a @code{size_t} or @code{ssize_t}, +or a @code{SCM} value. + +All objects of a given foreign type have the same number of slots. In +the example from the previous section, the @code{image} type has one +slot, because the slots list passed to +@code{scm_make_foreign_object_type} is of length one. (The actual names +given to slots are unimportant for most users of the C interface, but +can be used on the Scheme side to introspect on the foreign object.) + +To construct a foreign object and initialize its first slot, call +@code{scm_make_foreign_object_1 (@var{type}, @var{first_slot_value})}. +There are similarly named constructors for initializing 0, 1, 2, or 3 +slots, or initializing @var{n} slots via an array. @xref{Foreign +Objects}, for full details. Any fields that are not explicitly +initialized are set to 0. + +To get or set the value of a slot by index, you can use the +@code{scm_foreign_object_ref} and @code{scm_foreign_object_set_x} +functions. These functions take and return values as @code{void *} +pointers; there are corresponding convenience procedures like +@code{_signed_ref}, @code{_unsigned_set_x} and so on for dealing with +slots as signed or unsigned integers. + +Foreign objects fields that are pointers can be tricky to manage. If +possible, it is best that all memory that is referenced by a foreign +object be managed by the garbage collector. That way, the GC can +automatically ensure that memory is accessible when it is needed, and +freed when it becomes inaccessible. If this is not the case for your +program -- for example, if you are exposing an object to Scheme that was +allocated by some other, Guile-unaware part of your program -- then you +will probably need to implement a finalizer. @xref{Foreign Object +Memory Management}, for more. + +Continuing the example from the previous section, if the global variable +@code{image_type} contains the type returned by +@code{scm_make_foreign_object_type}, here is how we could construct a +foreign object whose ``data'' field contains a pointer to a freshly +allocated @code{struct image}: + +@example +SCM +make_image (SCM name, SCM s_width, SCM s_height) +@{ + struct image *image; + int width = scm_to_int (s_width); + int height = scm_to_int (s_height); + + /* Allocate the `struct image'. Because we + use scm_gc_malloc, this memory block will + be automatically reclaimed when it becomes + inaccessible, and its members will be traced + by the garbage collector. */ + image = (struct image *) + scm_gc_malloc (sizeof (struct image), "image"); + + image->width = width; + image->height = height; + + /* Allocating the pixels with + scm_gc_malloc_pointerless means that the + pixels data is collectable by GC, but + that GC shouldn't spend time tracing its + contents for nested pointers because there + aren't any. */ + image->pixels = + scm_gc_malloc_pointerless (width * height, "image pixels"); + + image->name = name; + image->update_func = SCM_BOOL_F; + + /* Now wrap the struct image* in a new foreign + object, and return that object. */ + return scm_make_foreign_object_1 (image_type, image); +@} +@end example + +We use @code{scm_gc_malloc_pointerless} for the pixel buffer to tell the +garbage collector not to scan it for pointers. Calls to +@code{scm_gc_malloc}, @code{scm_make_foreign_object_1}, and +@code{scm_gc_malloc_pointerless} raise an exception in out-of-memory +conditions; the garbage collector is able to reclaim previously +allocated memory if that happens. + + +@node Type Checking of Foreign Objects +@subsection Type Checking of Foreign Objects + +Functions that operate on foreign objects should check that the passed +@code{SCM} value indeed is of the correct type before accessing its +data. They can do this with @code{scm_assert_foreign_object_type}. + +For example, here is a simple function that operates on an image object, +and checks the type of its argument. + +@example +SCM +clear_image (SCM image_obj) +@{ + int area; + struct image *image; + + scm_assert_foreign_object_type (image_type, image_obj); + + image = scm_foreign_object_ref (image_obj, 0); + area = image->width * image->height; + memset (image->pixels, 0, area); + + /* Invoke the image's update function. */ + if (scm_is_true (image->update_func)) + scm_call_0 (image->update_func); + + return SCM_UNSPECIFIED; +@} +@end example + + +@node Foreign Object Memory Management +@subsection Foreign Object Memory Management + +Once a foreign object has been released to the tender mercies of the +Scheme system, it must be prepared to survive garbage collection. In +the example above, all the memory associated with the foreign object is +managed by the garbage collector because we used the @code{scm_gc_} +allocation functions. Thus, no special care must be taken: the garbage +collector automatically scans them and reclaims any unused memory. + +However, when data associated with a foreign object is managed in some +other way---e.g., @code{malloc}'d memory or file descriptors---it is +possible to specify a @dfn{finalizer} function to release those +resources when the foreign object is reclaimed. + +As discussed in @pxref{Garbage Collection}, Guile's garbage collector +will reclaim inaccessible memory as needed. This reclamation process +runs concurrently with the main program. When Guile analyzes the heap +and determines that an object's memory can be reclaimed, that memory is +put on a ``free list'' of objects that can be reclaimed. Usually that's +the end of it---the object is available for immediate re-use. However +some objects can have ``finalizers'' associated with them---functions +that are called on reclaimable objects to effect any external cleanup +actions. + +Finalizers are tricky business and it is best to avoid them. They can +be invoked at unexpected times, or not at all---for example, they are +not invoked on process exit. They don't help the garbage collector do +its job; in fact, they are a hindrance. Furthermore, they perturb the +garbage collector's internal accounting. The GC decides to scan the +heap when it thinks that it is necessary, after some amount of +allocation. Finalizable objects almost always represent an amount of +allocation that is invisible to the garbage collector. The effect can +be that the actual resource usage of a system with finalizable objects +is higher than what the GC thinks it should be. + +All those caveats aside, some foreign object types will need finalizers. +For example, if we had a foreign object type that wrapped file +descriptors---and we aren't suggesting this, as Guile already has ports +---then you might define the type like this: + +@example +static SCM file_type; + +static void +finalize_file (SCM file) +@{ + int fd = scm_foreign_object_signed_ref (file, 0); + if (fd >= 0) + @{ + scm_foreign_object_signed_set_x (file, 0, -1); + close (fd); + @} +@} + +static void +init_file_type (void) +@{ + SCM name, slots; + scm_t_struct_finalize finalizer; + + name = scm_from_utf8_symbol ("file"); + slots = scm_list_1 (scm_from_utf8_symbol ("fd")); + finalizer = finalize_file; + + image_type = + scm_make_foreign_object_type (name, slots, finalizer); +@} + +static SCM +make_file (int fd) +@{ + return scm_make_foreign_object_1 (file_type, (void *) fd); +@} +@end example + +@cindex finalizer +@cindex finalization + +Note that the finalizer may be invoked in ways and at times you might +not expect. In particular, if the user's Guile is built with support +for threads, the finalizer may be called from any thread that is running +Guile. In Guile 2.0, finalizers are invoked via ``asyncs'', which +interleaves them with running Scheme code; @pxref{System asyncs}. In +Guile 2.2 there will be a dedicated finalization thread, to ensure that +the finalization doesn't run within the critical section of any other +thread known to Guile. + +In either case, finalizers run concurrently with the main program, and +so they need to be async-safe and thread-safe. If for some reason this +is impossible, perhaps because you are embedding Guile in some +application that is not itself thread-safe, you have a few options. One +is to use guardians instead of finalizers, and arrange to pump the +guardians for finalizable objects. @xref{Guardians}, for more +information. The other option is to disable automatic finalization +entirely, and arrange to call @code{scm_run_finalizers ()} at +appropriate points. @xref{Foreign Objects}, for more on these +interfaces. + +Finalizers are allowed to allocate memory, access GC-managed memory, and +in general can do anything any Guile user code can do. This was not the +case in Guile 1.8, where finalizers were much more restricted. In +particular, in Guile 2.0, finalizers can resuscitate objects. We do not +recommend that users avail themselves of this possibility, however, as a +resuscitated object can re-expose other finalizable objects that have +been already finalized back to Scheme. These objects will not be +finalized again, but they could cause use-after-free problems to code +that handles objects of that particular foreign object type. To guard +against this possibility, robust finalization routines should clear +state from the foreign object, as in the above @code{free_file} example. + +One final caveat. Foreign object finalizers are associated with the +lifetime of a foreign object, not of its fields. If you access a field +of a finalizable foreign object, and do not arrange to keep a reference +on the foreign object itself, it could be that the outer foreign object +gets finalized while you are working with its field. + +For example, consider a procedure to read some data from a file, from +our example above. + +@example +SCM +read_bytes (SCM file, SCM n) +@{ + int fd; + SCM buf; + size_t len, pos; + + scm_assert_foreign_object_type (file_type, file); + + fd = scm_foreign_object_signed_ref (file, 0); + if (fd < 0) + scm_wrong_type_arg_msg ("read-bytes", SCM_ARG1, + file, "open file"); + + len = scm_to_size_t (n); + SCM buf = scm_c_make_bytevector (scm_to_size_t (n)); + + pos = 0; + while (pos < len) + @{ + char *bytes = SCM_BYTEVECTOR_CONTENTS (buf); + ssize_t count = read (fd, bytes + pos, len - pos); + if (count < 0) + scm_syserror ("read-bytes"); + if (count == 0) + break; + pos += count; + @} + + scm_remember_upto_here_1 (file); + + return scm_values (scm_list_2 (buf, scm_from_size_t (pos))); +@} +@end example + +After the prelude, only the @code{fd} value is used and the C compiler +has no reason to keep the @code{file} object around. If +@code{scm_c_make_bytevector} results in a garbage collection, +@code{file} might not be on the stack or anywhere else and could be +finalized, leaving @code{read} to read a closed (or, in a multi-threaded +program, possibly re-used) file descriptor. The use of +@code{scm_remember_upto_here_1} prevents this, by creating a reference +to @code{file} after all data accesses. @xref{Garbage Collection +Functions}. + +@code{scm_remember_upto_here_1} is only needed on finalizable objects, +because garbage collection of other values is invisible to the program +-- it happens when needed, and is not observable. But if you can, save +yourself the headache and build your program in such a way that it +doesn't need finalization. + + +@node Foreign Objects and Scheme +@subsection Foreign Objects and Scheme + +It is also possible to create foreign objects and object types from +Scheme, and to access fields of foreign objects from Scheme. For +example, the file example from the last section could be equivalently +expressed as: + +@example +(define-module (my-file) + #:use-module (system foreign-object) + #:use-module ((oop goops) #:select (make)) + #:export (make-file)) + +(define (finalize-file file) + (let ((fd (struct-ref file 0))) + (unless (< fd 0) + (struct-set! file 0 -1) + (close-fdes fd)))) + +(define <file> + (make-foreign-object-type '<file> '(fd) + #:finalizer finalize-file)) + +(define (make-file fd) + (make <file> #:fd fd)) +@end example + +Here we see that the result of @code{make-foreign-object-type}, which is +the equivalent of @code{scm_make_foreign_object_type}, is a struct +vtable. @xref{Vtables}, for more information. To instantiate the +foreign object, which is really a Guile struct, we use @code{make}. (We +could have used @code{make-struct/no-tail}, but as an implementation +detail, finalizers are attached in the @code{initialize} method called +by @code{make}). To access the fields, we use @code{struct-ref} and +@code{struct-set!}. @xref{Structure Basics}. + +There is a convenience syntax, @code{define-foreign-object-type}, that +defines a type along with a constructor, and getters for the fields. An +appropriate invocation of @code{define-foreign-object-type} for the +file object type could look like this: + +@example +(use-modules (system foreign-object)) + +(define-foreign-object-type <file> + make-file + (fd) + #:finalizer finalize-file) +@end example + +This defines the @code{<file>} type with one field, a @code{make-file} +constructor, and a getter for the @code{fd} field, bound to @code{fd}. + +Foreign object types are not only vtables but are actually GOOPS +classes, as hinted at above. @xref{GOOPS}, for more on Guile's +object-oriented programming system. Thus one can define print and +equality methods using GOOPS: + +@example +(use-modules (oop goops)) + +(define-method (write (file <file>) port) + ;; Assuming existence of the `fd' getter + (format port "#<<file> ~a>" (fd file))) + +(define-method (equal? (a <file>) (b <file>)) + (eqv? (fd a) (fd b))) +@end example + +One can even sub-class foreign types. + +@example +(define-class <named-file> (<file>) + (name #:init-keyword #:name #:init-value #f #:accessor name)) +@end example + +The question arises of how to construct these values, given that +@code{make-file} returns a plain old @code{<file>} object. It turns out +that you can use the GOOPS construction interface, where every field of +the foreign object has an associated initialization keyword argument. + +@example +(define* (my-open-file name #:optional (flags O_RDONLY)) + (make <named-file> #:fd (open-fdes name flags) #:name name)) + +(define-method (write (file <named-file>) port) + (format port "#<<file> ~s ~a>" (name file) (fd file))) +@end example + +@xref{Foreign Objects}, for full documentation on the Scheme interface +to foreign objects. @xref{GOOPS}, for more on GOOPS. + +As a final note, you might wonder how this system supports encapsulation +of sensitive values. First, we have to recognize that some facilities +are essentially unsafe and have global scope. For example, in C, the +integrity and confidentiality of a part of a program is at the mercy of +every other part of that program -- because any part of the program can +read and write anything in its address space. At the same time, +principled access to structured data is organized in C on lexical +boundaries; if you don't expose accessors for your object, you trust +other parts of the program not to work around that barrier. + +The situation is not dissimilar in Scheme. Although Scheme's unsafe +constructs are fewer in number than in C, they do exist. The +@code{(system foreign)} module can be used to violate confidentiality +and integrity, and shouldn't be exposed to untrusted code. Although +@code{struct-ref} and @code{struct-set!} are less unsafe, they still +have a cross-cutting capability of drilling through abstractions. +Performing a @code{struct-set!} on a foreign object slot could cause +unsafe foreign code to crash. Ultimately, structures in Scheme are +capabilities for abstraction, and not abstractions themselves. + +That leaves us with the lexical capabilities, like constructors and +accessors. Here is where encapsulation lies: the practical degree to +which the innards of your foreign objects are exposed is the degree to +which their accessors are lexically available in user code. If you want +to allow users to reference fields of your foreign object, provide them +with a getter. Otherwise you should assume that the only access to your +object may come from your code, which has the relevant authority, or via +code with access to cross-cutting @code{struct-ref} and such, which also +has the cross-cutting authority. diff --git a/doc/ref/libguile-program.texi b/doc/ref/libguile-program.texi index f565b916f..3b7408398 100644 --- a/doc/ref/libguile-program.texi +++ b/doc/ref/libguile-program.texi @@ -1,6 +1,6 @@ @c -*-texinfo-*- @c This is part of the GNU Guile Reference Manual. -@c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004, 2005 +@c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004, 2005, 2014 @c Free Software Foundation, Inc. @c See the file guile.texi for copying conditions. @@ -46,7 +46,7 @@ applications in general. @menu * Dia Objective:: Deciding why you want to add Guile. * Dia Steps:: Four steps required to add Guile. -* Dia Smobs:: How to represent Dia data in Scheme. +* Dia Objects:: How to represent Dia data in Scheme. * Dia Primitives:: Writing Guile primitives for Dia. * Dia Hook:: Providing a hook for Scheme evaluation. * Dia Structure:: Overall structure for adding Guile. @@ -115,8 +115,8 @@ First, you need a way of representing your application-specific objects --- such as @code{shape} in the previous example --- when they are passed into the Scheme world. Unless your objects are so simple that they map naturally into builtin Scheme data types like numbers and -strings, you will probably want to use Guile's @dfn{SMOB} interface to -create a new Scheme data type for your objects. +strings, you will probably want to use Guile's @dfn{foreign object} +interface to create a new Scheme data type for your objects. Second, you need to write code for the basic operations like @code{for-each-shape} and @code{square?} such that they access and @@ -129,17 +129,18 @@ evaluated. Finally, you need to restructure your top-level application C code a little so that it initializes the Guile interpreter correctly and -declares your @dfn{SMOBs} and @dfn{primitives} to the Scheme world. +declares your @dfn{foreign objects} and @dfn{primitives} to the Scheme +world. The following subsections expand on these four points in turn. -@node Dia Smobs +@node Dia Objects @subsubsection How to Represent Dia Data in Scheme For all but the most trivial applications, you will probably want to allow some representation of your domain objects to exist on the Scheme -level. This is where the idea of SMOBs comes in, and with it issues of +level. This is where foreign objects come in, and with them issues of lifetime management and garbage collection. To get more concrete about this, let's look again at the example we gave @@ -189,21 +190,21 @@ finished evaluation. How do we avoid this happening? @end itemize One resolution of these issues is for the Scheme-level representation of -a shape to be a new, Scheme-specific C structure wrapped up as a SMOB. -The SMOB is what is passed into and out of Scheme code, and the -Scheme-specific C structure inside the SMOB points to Dia's underlying C -structure so that the code for primitives like @code{square?} can get at -it. +a shape to be a new, Scheme-specific C structure wrapped up as a foreign +object. The foreign object is what is passed into and out of Scheme +code, and the Scheme-specific C structure inside the foreign object +points to Dia's underlying C structure so that the code for primitives +like @code{square?} can get at it. To cope with an underlying shape being deleted while Scheme code is still holding onto a Scheme shape value, the underlying C structure -should have a new field that points to the Scheme-specific SMOB. When a -shape is deleted, the relevant code chains through to the -Scheme-specific structure and sets its pointer back to the underlying -structure to NULL. Thus the SMOB value for the shape continues to -exist, but any primitive code that tries to use it will detect that the -underlying shape has been deleted because the underlying structure -pointer is NULL. +should have a new field that points to the Scheme-specific foreign +object. When a shape is deleted, the relevant code chains through to +the Scheme-specific structure and sets its pointer back to the +underlying structure to NULL. Thus the foreign object value for the +shape continues to exist, but any primitive code that tries to use it +will detect that the underlying shape has been deleted because the +underlying structure pointer is NULL. So, to summarize the steps involved in this resolution of the problem (and assuming that the underlying C structure for a shape is @@ -238,33 +239,33 @@ struct dia_shape underlying shape is deleted. @item -Wrap @code{struct dia_guile_shape} as a SMOB type. +Wrap @code{struct dia_guile_shape} as a foreign object type. @item Whenever you need to represent a C shape onto the Scheme level, create a -SMOB instance for it, and pass that. +foreign object instance for it, and pass that. @item -In primitive code that receives a shape SMOB instance, check the +In primitive code that receives a shape foreign object instance, check the @code{c_shape} field when decoding it, to find out whether the underlying C shape is still there. @end itemize -As far as memory management is concerned, the SMOB values and their -Scheme-specific structures are under the control of the garbage +As far as memory management is concerned, the foreign object values and +their Scheme-specific structures are under the control of the garbage collector, whereas the underlying C structures are explicitly managed in exactly the same way that Dia managed them before we thought of adding Guile. -When the garbage collector decides to free a shape SMOB value, it calls -the @dfn{SMOB free} function that was specified when defining the shape -SMOB type. To maintain the correctness of the @code{guile_shape} field -in the underlying C structure, this function should chain through to the -underlying C structure (if it still exists) and set its -@code{guile_shape} field to NULL. +When the garbage collector decides to free a shape foreign object value, +it calls the @dfn{finalizer} function that was specified when defining +the shape foreign object type. To maintain the correctness of the +@code{guile_shape} field in the underlying C structure, this function +should chain through to the underlying C structure (if it still exists) +and set its @code{guile_shape} field to NULL. -For full documentation on defining and using SMOB types, see -@ref{Defining New Types (Smobs)}. +For full documentation on defining and using foreign object types, see +@ref{Defining New Foreign Object Types}. @node Dia Primitives @@ -283,11 +284,11 @@ static SCM square_p (SCM shape) @{ struct dia_guile_shape * guile_shape; - /* Check that arg is really a shape SMOB. */ - scm_assert_smob_type (shape_tag, shape); + /* Check that arg is really a shape object. */ + scm_assert_foreign_object_type (shape_type, shape); /* Access Scheme-specific shape structure. */ - guile_shape = SCM_SMOB_DATA (shape); + guile_shape = scm_foreign_object_ref (shape, 0); /* Find out if underlying shape exists and is a square; return answer as a Scheme boolean. */ @@ -297,26 +298,28 @@ static SCM square_p (SCM shape) @end lisp Notice how easy it is to chain through from the @code{SCM shape} -parameter that @code{square_p} receives --- which is a SMOB --- to the -Scheme-specific structure inside the SMOB, and thence to the underlying -C structure for the shape. - -In this code, @code{scm_assert_smob_type}, @code{SCM_SMOB_DATA}, and -@code{scm_from_bool} are from the standard Guile API. We assume that -@code{shape_tag} was given to us when we made the shape SMOB type, using -@code{scm_make_smob_type}. The call to @code{scm_assert_smob_type} -ensures that @var{shape} is indeed a shape. This is needed to guard -against Scheme code using the @code{square?} procedure incorrectly, as -in @code{(square? "hello")}; Scheme's latent typing means that usage -errors like this must be caught at run time. +parameter that @code{square_p} receives --- which is a foreign object +--- to the Scheme-specific structure inside the foreign object, and +thence to the underlying C structure for the shape. + +In this code, @code{scm_assert_foreign_object_type}, +@code{scm_foreign_object_ref}, and @code{scm_from_bool} are from the +standard Guile API. We assume that @code{shape_type} was given to us +when we made the shape foreign object type, using +@code{scm_make_foreign_object_type}. The call to +@code{scm_assert_foreign_object_type} ensures that @var{shape} is indeed +a shape. This is needed to guard against Scheme code using the +@code{square?} procedure incorrectly, as in @code{(square? "hello")}; +Scheme's latent typing means that usage errors like this must be caught +at run time. Having written the C code for your primitives, you need to make them available as Scheme procedures by calling the @code{scm_c_define_gsubr} -function. @code{scm_c_define_gsubr} (@pxref{Primitive Procedures}) takes arguments that -specify the Scheme-level name for the primitive and how many required, -optional and rest arguments it can accept. The @code{square?} primitive -always requires exactly one argument, so the call to make it available -in Scheme reads like this: +function. @code{scm_c_define_gsubr} (@pxref{Primitive Procedures}) +takes arguments that specify the Scheme-level name for the primitive and +how many required, optional and rest arguments it can accept. The +@code{square?} primitive always requires exactly one argument, so the +call to make it available in Scheme reads like this: @lisp scm_c_define_gsubr ("square?", 1, 0, 0, square_p); @@ -384,7 +387,7 @@ do lots of initialization and setup stuff @itemize @bullet @item -define all SMOB types +define all foreign object types @item export primitives to Scheme using @code{scm_c_define_gsubr} @item @@ -397,13 +400,13 @@ In other words, you move the guts of what was previously in your then add a @code{scm_boot_guile} call, with @code{inner_main} as a parameter, to the end of @code{main}. -Assuming that you are using SMOBs and have written primitive code as -described in the preceding subsections, you also need to insert calls to -declare your new SMOBs and export the primitives to Scheme. These -declarations must happen @emph{inside} the dynamic scope of the -@code{scm_boot_guile} call, but also @emph{before} any code is run that -could possibly use them --- the beginning of @code{inner_main} is an -ideal place for this. +Assuming that you are using foreign objects and have written primitive +code as described in the preceding subsections, you also need to insert +calls to declare your new foreign objects and export the primitives to +Scheme. These declarations must happen @emph{inside} the dynamic scope +of the @code{scm_boot_guile} call, but also @emph{before} any code is +run that could possibly use them --- the beginning of @code{inner_main} +is an ideal place for this. @node Dia Advanced @@ -425,7 +428,8 @@ move the code that lays out and displays Dia objects from C to Scheme. As you follow this path, it naturally becomes less useful to maintain a distinction between Dia's original non-Guile-related source code, and -its later code implementing SMOBs and primitives for the Scheme world. +its later code implementing foreign objects and primitives for the +Scheme world. For example, suppose that the original source code had a @code{dia_change_fill_pattern} function: @@ -440,8 +444,8 @@ void dia_change_fill_pattern (struct dia_shape * shape, During initial Guile integration, you add a @code{change_fill_pattern} primitive for Scheme purposes, which accesses the underlying structures -from its SMOB values and uses @code{dia_change_fill_pattern} to do the -real work: +from its foreign object values and uses @code{dia_change_fill_pattern} +to do the real work: @lisp SCM change_fill_pattern (SCM shape, SCM pattern) @@ -487,22 +491,23 @@ So further Guile integration progressively @emph{reduces} the amount of functional C code that you have to maintain over the long term. A similar argument applies to data representation. In the discussion of -SMOBs earlier, issues arose because of the different memory management -and lifetime models that normally apply to data structures in C and in -Scheme. However, with further Guile integration, you can resolve this -issue in a more radical way by allowing all your data structures to be -under the control of the garbage collector, and kept alive by references -from the Scheme world. Instead of maintaining an array or linked list -of shapes in C, you would instead maintain a list in Scheme. +foreign objects earlier, issues arose because of the different memory +management and lifetime models that normally apply to data structures in +C and in Scheme. However, with further Guile integration, you can +resolve this issue in a more radical way by allowing all your data +structures to be under the control of the garbage collector, and kept +alive by references from the Scheme world. Instead of maintaining an +array or linked list of shapes in C, you would instead maintain a list +in Scheme. Rather like the coalescing of @code{dia_change_fill_pattern} and @code{change_fill_pattern}, the practical upshot of such a change is that you would no longer have to keep the @code{dia_shape} and @code{dia_guile_shape} structures separate, and so wouldn't need to worry about the pointers between them. Instead, you could change the -SMOB definition to wrap the @code{dia_shape} structure directly, and -send @code{dia_guile_shape} off to the scrap yard. Cut out the middle -man! +foreign object definition to wrap the @code{dia_shape} structure +directly, and send @code{dia_guile_shape} off to the scrap yard. Cut +out the middle man! Finally, we come to the holy grail of Guile's free software / extension language approach. Once you have a Scheme representation for diff --git a/doc/ref/libguile-smobs.texi b/doc/ref/libguile-smobs.texi deleted file mode 100644 index d68b71812..000000000 --- a/doc/ref/libguile-smobs.texi +++ /dev/null @@ -1,670 +0,0 @@ -@c -*-texinfo-*- -@c This is part of the GNU Guile Reference Manual. -@c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004, 2005, 2010, 2011, 2013, 2014 -@c Free Software Foundation, Inc. -@c See the file guile.texi for copying conditions. - -@node Defining New Types (Smobs) -@section Defining New Types (Smobs) - -@dfn{Smobs} are Guile's mechanism for adding new primitive types to -the system. The term ``smob'' was coined by Aubrey Jaffer, who says -it comes from ``small object'', referring to the fact that they are -quite limited in size: they can hold just one pointer to a larger -memory block plus 16 extra bits. - -To define a new smob type, the programmer provides Guile with some -essential information about the type --- how to print it, how to -garbage collect it, and so on --- and Guile allocates a fresh type tag -for it. The programmer can then use @code{scm_c_define_gsubr} to make -a set of C functions visible to Scheme code that create and operate on -these objects. - -(You can find a complete version of the example code used in this -section in the Guile distribution, in @file{doc/example-smob}. That -directory includes a makefile and a suitable @code{main} function, so -you can build a complete interactive Guile shell, extended with the -datatypes described here.) - -@menu -* Describing a New Type:: -* Creating Smob Instances:: -* Type checking:: -* Garbage Collecting Smobs:: -* Remembering During Operations:: -* Double Smobs:: -* The Complete Example:: -@end menu - -@node Describing a New Type -@subsection Describing a New Type - -To define a new type, the programmer must write two functions to -manage instances of the type: - -@table @code -@item print -Guile will apply this function to each instance of the new type to print -the value, as for @code{display} or @code{write}. The default print -function prints @code{#<NAME ADDRESS>} where @code{NAME} is the first -argument passed to @code{scm_make_smob_type}. - -@item equalp -If Scheme code asks the @code{equal?} function to compare two instances -of the same smob type, Guile calls this function. It should return -@code{SCM_BOOL_T} if @var{a} and @var{b} should be considered -@code{equal?}, or @code{SCM_BOOL_F} otherwise. If @code{equalp} is -@code{NULL}, @code{equal?} will assume that two instances of this type are -never @code{equal?} unless they are @code{eq?}. - -@end table - -When the only resource associated with a smob is memory managed by the -garbage collector---i.e., memory allocated with the @code{scm_gc_malloc} -functions---this is sufficient. However, when a smob is associated with -other kinds of resources, it may be necessary to define one of the -following functions, or both: - -@table @code -@item mark -Guile will apply this function to each instance of the new type it -encounters during garbage collection. This function is responsible for -telling the collector about any other @code{SCM} values that the object -has stored, and that are in memory regions not already scanned by the -garbage collector. @xref{Garbage Collecting Smobs}, for more details. - -@item free -Guile will apply this function to each instance of the new type that is -to be deallocated. The function should release all resources held by -the object. This is analogous to the Java finalization method---it is -invoked at an unspecified time (when garbage collection occurs) after -the object is dead. @xref{Garbage Collecting Smobs}, for more details. - -This function operates while the heap is in an inconsistent state and -must therefore be careful. @xref{Smobs}, for details about what this -function is allowed to do. -@end table - -To actually register the new smob type, call @code{scm_make_smob_type}. -It returns a value of type @code{scm_t_bits} which identifies the new -smob type. - -The four special functions described above are registered by calling -one of @code{scm_set_smob_mark}, @code{scm_set_smob_free}, -@code{scm_set_smob_print}, or @code{scm_set_smob_equalp}, as -appropriate. Each function is intended to be used at most once per -type, and the call should be placed immediately following the call to -@code{scm_make_smob_type}. - -There can only be at most 256 different smob types in the system. -Instead of registering a huge number of smob types (for example, one -for each relevant C struct in your application), it is sometimes -better to register just one and implement a second layer of type -dispatching on top of it. This second layer might use the 16 extra -bits to extend its type, for example. - -Here is how one might declare and register a new type representing -eight-bit gray-scale images: - -@example -#include <libguile.h> - -struct image @{ - int width, height; - char *pixels; - - /* The name of this image */ - SCM name; - - /* A function to call when this image is - modified, e.g., to update the screen, - or SCM_BOOL_F if no action necessary */ - SCM update_func; -@}; - -static scm_t_bits image_tag; - -void -init_image_type (void) -@{ - image_tag = scm_make_smob_type ("image", sizeof (struct image)); - scm_set_smob_mark (image_tag, mark_image); - scm_set_smob_free (image_tag, free_image); - scm_set_smob_print (image_tag, print_image); -@} -@end example - - -@node Creating Smob Instances -@subsection Creating Smob Instances - -Normally, smobs can have one @emph{immediate} word of data. This word -stores either a pointer to an additional memory block that holds the -real data, or it might hold the data itself when it fits. The word is -large enough for a @code{SCM} value, a pointer to @code{void}, or an -integer that fits into a @code{size_t} or @code{ssize_t}. - -You can also create smobs that have two or three immediate words, and -when these words suffice to store all data, it is more efficient to use -these super-sized smobs instead of using a normal smob plus a memory -block. @xref{Double Smobs}, for their discussion. - -Guile provides functions for managing memory which are often helpful -when implementing smobs. @xref{Memory Blocks}. - -To retrieve the immediate word of a smob, you use the macro -@code{SCM_SMOB_DATA}. It can be set with @code{SCM_SET_SMOB_DATA}. -The 16 extra bits can be accessed with @code{SCM_SMOB_FLAGS} and -@code{SCM_SET_SMOB_FLAGS}. - -The two macros @code{SCM_SMOB_DATA} and @code{SCM_SET_SMOB_DATA} treat -the immediate word as if it were of type @code{scm_t_bits}, which is -an unsigned integer type large enough to hold a pointer to -@code{void}. Thus you can use these macros to store arbitrary -pointers in the smob word. - -When you want to store a @code{SCM} value directly in the immediate -word of a smob, you should use the macros @code{SCM_SMOB_OBJECT} and -@code{SCM_SET_SMOB_OBJECT} to access it. - -Creating a smob instance can be tricky when it consists of multiple -steps that allocate resources. Most of the time, this is mainly about -allocating memory to hold associated data structures. Using memory -managed by the garbage collector simplifies things: the garbage -collector will automatically scan those data structures for pointers, -and reclaim them when they are no longer referenced. - -Continuing the example from above, if the global variable -@code{image_tag} contains a tag returned by @code{scm_make_smob_type}, -here is how we could construct a smob whose immediate word contains a -pointer to a freshly allocated @code{struct image}: - -@example -SCM -make_image (SCM name, SCM s_width, SCM s_height) -@{ - SCM smob; - struct image *image; - int width = scm_to_int (s_width); - int height = scm_to_int (s_height); - - /* Step 1: Allocate the memory block. - */ - image = (struct image *) - scm_gc_malloc (sizeof (struct image), "image"); - - /* Step 2: Initialize it with straight code. - */ - image->width = width; - image->height = height; - image->pixels = NULL; - image->name = SCM_BOOL_F; - image->update_func = SCM_BOOL_F; - - /* Step 3: Create the smob. - */ - smob = scm_new_smob (image_tag, image); - - /* Step 4: Finish the initialization. - */ - image->name = name; - image->pixels = - scm_gc_malloc_pointerless (width * height, "image pixels"); - - return smob; -@} -@end example - -We use @code{scm_gc_malloc_pointerless} for the pixel buffer to tell the -garbage collector not to scan it for pointers. Calls to -@code{scm_gc_malloc}, @code{scm_new_smob}, and -@code{scm_gc_malloc_pointerless} raise an exception in out-of-memory -conditions; the garbage collector is able to reclaim previously -allocated memory if that happens. - - -@node Type checking -@subsection Type checking - -Functions that operate on smobs should check that the passed -@code{SCM} value indeed is a suitable smob before accessing its data. -They can do this with @code{scm_assert_smob_type}. - -For example, here is a simple function that operates on an image smob, -and checks the type of its argument. - -@example -SCM -clear_image (SCM image_smob) -@{ - int area; - struct image *image; - - scm_assert_smob_type (image_tag, image_smob); - - image = (struct image *) SCM_SMOB_DATA (image_smob); - area = image->width * image->height; - memset (image->pixels, 0, area); - - /* Invoke the image's update function. - */ - if (scm_is_true (image->update_func)) - scm_call_0 (image->update_func); - - scm_remember_upto_here_1 (image_smob); - - return SCM_UNSPECIFIED; -@} -@end example - -See @ref{Remembering During Operations} for an explanation of the call -to @code{scm_remember_upto_here_1}. - - -@node Garbage Collecting Smobs -@subsection Garbage Collecting Smobs - -Once a smob has been released to the tender mercies of the Scheme -system, it must be prepared to survive garbage collection. In the -example above, all the memory associated with the smob is managed by the -garbage collector because we used the @code{scm_gc_} allocation -functions. Thus, no special care must be taken: the garbage collector -automatically scans them and reclaims any unused memory. - -However, when data associated with a smob is managed in some other -way---e.g., @code{malloc}'d memory or file descriptors---it is possible -to specify a @emph{free} function to release those resources when the -smob is reclaimed, and a @emph{mark} function to mark Scheme objects -otherwise invisible to the garbage collector. - -As described in more detail elsewhere (@pxref{Conservative GC}), every -object in the Scheme system has a @dfn{mark bit}, which the garbage -collector uses to tell live objects from dead ones. When collection -starts, every object's mark bit is clear. The collector traces pointers -through the heap, starting from objects known to be live, and sets the -mark bit on each object it encounters. When it can find no more -unmarked objects, the collector walks all objects, live and dead, frees -those whose mark bits are still clear, and clears the mark bit on the -others. - -The two main portions of the collection are called the @dfn{mark phase}, -during which the collector marks live objects, and the @dfn{sweep -phase}, during which the collector frees all unmarked objects. - -The mark bit of a smob lives in a special memory region. When the -collector encounters a smob, it sets the smob's mark bit, and uses the -smob's type tag to find the appropriate @emph{mark} function for that -smob. It then calls this @emph{mark} function, passing it the smob as -its only argument. - -The @emph{mark} function is responsible for marking any other Scheme -objects the smob refers to. If it does not do so, the objects' mark -bits will still be clear when the collector begins to sweep, and the -collector will free them. If this occurs, it will probably break, or at -least confuse, any code operating on the smob; the smob's @code{SCM} -values will have become dangling references. - -To mark an arbitrary Scheme object, the @emph{mark} function calls -@code{scm_gc_mark}. - -Thus, here is how we might write @code{mark_image}---again this is not -needed in our example since we used the @code{scm_gc_} allocation -routines, so this is just for the sake of illustration: - -@example -@group -SCM -mark_image (SCM image_smob) -@{ - /* Mark the image's name and update function. */ - struct image *image = (struct image *) SCM_SMOB_DATA (image_smob); - - scm_gc_mark (image->name); - scm_gc_mark (image->update_func); - - return SCM_BOOL_F; -@} -@end group -@end example - -Note that, even though the image's @code{update_func} could be an -arbitrarily complex structure (representing a procedure and any values -enclosed in its environment), @code{scm_gc_mark} will recurse as -necessary to mark all its components. Because @code{scm_gc_mark} sets -an object's mark bit before it recurses, it is not confused by -circular structures. - -As an optimization, the collector will mark whatever value is returned -by the @emph{mark} function; this helps limit depth of recursion during -the mark phase. Thus, the code above should really be written as: -@example -@group -SCM -mark_image (SCM image_smob) -@{ - /* Mark the image's name and update function. */ - struct image *image = (struct image *) SCM_SMOB_DATA (image_smob); - - scm_gc_mark (image->name); - return image->update_func; -@} -@end group -@end example - - -Finally, when the collector encounters an unmarked smob during the sweep -phase, it uses the smob's tag to find the appropriate @emph{free} -function for the smob. It then calls that function, passing it the smob -as its only argument. - -The @emph{free} function must release any resources used by the smob. -However, it must not free objects managed by the collector; the -collector will take care of them. For historical reasons, the return -type of the @emph{free} function should be @code{size_t}, an unsigned -integral type; the @emph{free} function should always return zero. - -Here is how we might write the @code{free_image} function for the image -smob type---again for the sake of illustration, since our example does -not need it thanks to the use of the @code{scm_gc_} allocation routines: -@example -size_t -free_image (SCM image_smob) -@{ - struct image *image = (struct image *) SCM_SMOB_DATA (image_smob); - - scm_gc_free (image->pixels, - image->width * image->height, - "image pixels"); - scm_gc_free (image, sizeof (struct image), "image"); - - return 0; -@} -@end example - -During the sweep phase, the garbage collector will clear the mark bits -on all live objects. The code which implements a smob need not do this -itself. - -@cindex finalizer -@cindex finalization - -Note that the free function can be called in any context. In -particular, if your Guile is built with support for threads, the -finalizer will be called from a dedicated finalization thread. This -ensures that the finalization doesn't run within the critical section of -any other thread known to Guile. It also lowers latency, as your Guile -program doesn't have to wait for finalizers to run. However, if your -Guile is built without threads, the finalizers may be called within the -critical section of some other piece of code. - -In either case, finalizers (free functions) run concurrently with the -main program, and so they need to be thread-safe. If for some reason -this is impossible, perhaps because you are embedding Guile in some -application that is not itself thread-safe, you have a few options. One -is to use guardians instead of free functions, and arrange to pump the -guardians for finalizable objects. @xref{Guardians}, for more -information. The other option is to disable automatic finalization -entirely, and arrange to call @code{scm_run_finalizers ()} at -appropriate points. @xref{Smobs}, for more on these interfaces. - -There is no way for smob code to be notified when collection is -complete. - -It is usually a good idea to minimize the amount of processing done -during garbage collection; keep the @emph{mark} and @emph{free} -functions very simple. Since collections occur at unpredictable times, -it is easy for any unusual activity to interfere with normal code. - -@node Remembering During Operations -@subsection Remembering During Operations -@cindex remembering - -@c FIXME: Remove this section? - -It's important that a smob is visible to the garbage collector -whenever its contents are being accessed. Otherwise it could be freed -while code is still using it. - -For example, consider a procedure to convert image data to a list of -pixel values. - -@example -SCM -image_to_list (SCM image_smob) -@{ - struct image *image; - SCM lst; - int i; - - scm_assert_smob_type (image_tag, image_smob); - - image = (struct image *) SCM_SMOB_DATA (image_smob); - lst = SCM_EOL; - for (i = image->width * image->height - 1; i >= 0; i--) - lst = scm_cons (scm_from_char (image->pixels[i]), lst); - - scm_remember_upto_here_1 (image_smob); - return lst; -@} -@end example - -In the loop, only the @code{image} pointer is used and the C compiler -has no reason to keep the @code{image_smob} value anywhere. If -@code{scm_cons} results in a garbage collection, @code{image_smob} might -not be on the stack or anywhere else and could be freed, leaving the -loop accessing freed data. The use of @code{scm_remember_upto_here_1} -prevents this, by creating a reference to @code{image_smob} after all -data accesses. - -There's no need to do the same for @code{lst}, since that's the return -value and the compiler will certainly keep it in a register or -somewhere throughout the routine. - -The @code{clear_image} example previously shown (@pxref{Type checking}) -also used @code{scm_remember_upto_here_1} for this reason. - -It's only in quite rare circumstances that a missing -@code{scm_remember_upto_here_1} will bite, but when it happens the -consequences are serious. Fortunately the rule is simple: whenever -calling a Guile library function or doing something that might, ensure -that the @code{SCM} of a smob is referenced past all accesses to its -insides. Do this by adding an @code{scm_remember_upto_here_1} if -there are no other references. - -In a multi-threaded program, the rule is the same. As far as a given -thread is concerned, a garbage collection still only occurs within a -Guile library function, not at an arbitrary time. (Guile waits for all -threads to reach one of its library functions, and holds them there -while the collector runs.) - -@node Double Smobs -@subsection Double Smobs - -@c FIXME: Remove this section? - -Smobs are called smob because they are small: they normally have only -room for one @code{void*} or @code{SCM} value plus 16 bits. The -reason for this is that smobs are directly implemented by using the -low-level, two-word cells of Guile that are also used to implement -pairs, for example. (@pxref{Data Representation} for the -details.) One word of the two-word cells is used for -@code{SCM_SMOB_DATA} (or @code{SCM_SMOB_OBJECT}), the other contains -the 16-bit type tag and the 16 extra bits. - -In addition to the fundamental two-word cells, Guile also has -four-word cells, which are appropriately called @dfn{double cells}. -You can use them for @dfn{double smobs} and get two more immediate -words of type @code{scm_t_bits}. - -A double smob is created with @code{scm_new_double_smob}. Its immediate -words can be retrieved as @code{scm_t_bits} with @code{SCM_SMOB_DATA_2} -and @code{SCM_SMOB_DATA_3} in addition to @code{SCM_SMOB_DATA}. -Unsurprisingly, the words can be set to @code{scm_t_bits} values with -@code{SCM_SET_SMOB_DATA_2} and @code{SCM_SET_SMOB_DATA_3}. - -Of course there are also @code{SCM_SMOB_OBJECT_2}, -@code{SCM_SMOB_OBJECT_3}, @code{SCM_SET_SMOB_OBJECT_2}, and -@code{SCM_SET_SMOB_OBJECT_3}. - -@node The Complete Example -@subsection The Complete Example - -Here is the complete text of the implementation of the image datatype, -as presented in the sections above. We also provide a definition for -the smob's @emph{print} function, and make some objects and functions -static, to clarify exactly what the surrounding code is using. - -As mentioned above, you can find this code in the Guile distribution, in -@file{doc/example-smob}. That directory includes a makefile and a -suitable @code{main} function, so you can build a complete interactive -Guile shell, extended with the datatypes described here.) - -@example -/* file "image-type.c" */ - -#include <stdlib.h> -#include <libguile.h> - -static scm_t_bits image_tag; - -struct image @{ - int width, height; - char *pixels; - - /* The name of this image */ - SCM name; - - /* A function to call when this image is - modified, e.g., to update the screen, - or SCM_BOOL_F if no action necessary */ - SCM update_func; -@}; - -static SCM -make_image (SCM name, SCM s_width, SCM s_height) -@{ - SCM smob; - struct image *image; - int width = scm_to_int (s_width); - int height = scm_to_int (s_height); - - /* Step 1: Allocate the memory block. - */ - image = (struct image *) - scm_gc_malloc (sizeof (struct image), "image"); - - /* Step 2: Initialize it with straight code. - */ - image->width = width; - image->height = height; - image->pixels = NULL; - image->name = SCM_BOOL_F; - image->update_func = SCM_BOOL_F; - - /* Step 3: Create the smob. - */ - smob = scm_new_smob (image_tag, image); - - /* Step 4: Finish the initialization. - */ - image->name = name; - image->pixels = - scm_gc_malloc (width * height, "image pixels"); - - return smob; -@} - -SCM -clear_image (SCM image_smob) -@{ - int area; - struct image *image; - - scm_assert_smob_type (image_tag, image_smob); - - image = (struct image *) SCM_SMOB_DATA (image_smob); - area = image->width * image->height; - memset (image->pixels, 0, area); - - /* Invoke the image's update function. - */ - if (scm_is_true (image->update_func)) - scm_call_0 (image->update_func); - - scm_remember_upto_here_1 (image_smob); - - return SCM_UNSPECIFIED; -@} - -static SCM -mark_image (SCM image_smob) -@{ - /* Mark the image's name and update function. */ - struct image *image = (struct image *) SCM_SMOB_DATA (image_smob); - - scm_gc_mark (image->name); - return image->update_func; -@} - -static size_t -free_image (SCM image_smob) -@{ - struct image *image = (struct image *) SCM_SMOB_DATA (image_smob); - - scm_gc_free (image->pixels, - image->width * image->height, - "image pixels"); - scm_gc_free (image, sizeof (struct image), "image"); - - return 0; -@} - -static int -print_image (SCM image_smob, SCM port, scm_print_state *pstate) -@{ - struct image *image = (struct image *) SCM_SMOB_DATA (image_smob); - - scm_puts ("#<image ", port); - scm_display (image->name, port); - scm_puts (">", port); - - /* non-zero means success */ - return 1; -@} - -void -init_image_type (void) -@{ - image_tag = scm_make_smob_type ("image", sizeof (struct image)); - scm_set_smob_mark (image_tag, mark_image); - scm_set_smob_free (image_tag, free_image); - scm_set_smob_print (image_tag, print_image); - - scm_c_define_gsubr ("clear-image", 1, 0, 0, clear_image); - scm_c_define_gsubr ("make-image", 3, 0, 0, make_image); -@} -@end example - -Here is a sample build and interaction with the code from the -@file{example-smob} directory, on the author's machine: - -@example -zwingli:example-smob$ make CC=gcc -gcc `pkg-config --cflags guile-@value{EFFECTIVE-VERSION}` -c image-type.c -o image-type.o -gcc `pkg-config --cflags guile-@value{EFFECTIVE-VERSION}` -c myguile.c -o myguile.o -gcc image-type.o myguile.o `pkg-config --libs guile-@value{EFFECTIVE-VERSION}` -o myguile -zwingli:example-smob$ ./myguile -guile> make-image -#<primitive-procedure make-image> -guile> (define i (make-image "Whistler's Mother" 100 100)) -guile> i -#<image Whistler's Mother> -guile> (clear-image i) -guile> (clear-image 4) -ERROR: In procedure clear-image in expression (clear-image 4): -ERROR: Wrong type (expecting image): 4 -ABORT: (wrong-type-arg) - -Type "(backtrace)" to get more information. -guile> -@end example diff --git a/doc/ref/libguile-snarf.texi b/doc/ref/libguile-snarf.texi index c70727f2d..9b0e42fa3 100644 --- a/doc/ref/libguile-snarf.texi +++ b/doc/ref/libguile-snarf.texi @@ -1,6 +1,6 @@ @c -*-texinfo-*- @c This is part of the GNU Guile Reference Manual. -@c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004, 2012 +@c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004, 2012, 2014 @c Free Software Foundation, Inc. @c See the file guile.texi for copying conditions. @@ -61,10 +61,10 @@ implemented by the C function @code{clear_image}: #include <libguile.h> SCM_DEFINE (clear_image, "clear-image", 1, 0, 0, - (SCM image_smob), + (SCM image), "Clear the image.") @{ - /* C code to clear the image in @code{image_smob}... */ + /* C code to clear the image in @code{image}... */ @} void @@ -78,9 +78,9 @@ init_image_type () The @code{SCM_DEFINE} declaration says that the C function @code{clear_image} implements a Scheme function called @code{clear-image}, which takes one required argument (of type -@code{SCM} and named @code{image_smob}), no optional arguments, and no -rest argument. The string @code{"Clear the image."} provides a short -help text for the function, it is called a @dfn{docstring}. +@code{SCM} and named @code{image}), no optional arguments, and no rest +argument. The string @code{"Clear the image."} provides a short help +text for the function, it is called a @dfn{docstring}. @code{SCM_DEFINE} macro also defines a static array of characters initialized to the Scheme name of the function. In this case, diff --git a/doc/ref/tools.texi b/doc/ref/tools.texi index 2c624936f..e962a86ab 100644 --- a/doc/ref/tools.texi +++ b/doc/ref/tools.texi @@ -1,6 +1,6 @@ @c -*-texinfo-*- @c This is part of the GNU Guile Reference Manual. -@c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004, 2011 +@c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004, 2011, 2014 @c Free Software Foundation, Inc. @c See the file guile.texi for copying conditions. @@ -112,11 +112,11 @@ For example, here is how you might define a new subr called #include <libguile.h> SCM_DEFINE (clear_image, "clear-image", 1, 0, 0, - (SCM image_smob), + (SCM image), "Clear the image.") #define FUNC_NAME s_clear_image @{ - /* C code to clear the image in @code{image_smob}... */ + /* C code to clear the image in @code{image}... */ @} #undef FUNC_NAME @@ -131,8 +131,8 @@ init_image_type () The @code{SCM_DEFINE} declaration says that the C function @code{clear_image} implements a Scheme subr called @code{clear-image}, which takes one required argument (of type @code{SCM} and named -@code{image_smob}), no optional arguments, and no rest argument. -@xref{Doc Snarfing}, for info on the docstring. +@code{image}), no optional arguments, and no rest argument. @xref{Doc +Snarfing}, for info on the docstring. This works in concert with @code{FUNC_NAME} to also define a static array of characters named @code{s_clear_image}, initialized to the diff --git a/libguile.h b/libguile.h index b067b28a5..4904d6980 100644 --- a/libguile.h +++ b/libguile.h @@ -1,7 +1,7 @@ #ifndef SCM_LIBGUILE_H #define SCM_LIBGUILE_H -/* Copyright (C) 1995,1996,1997,1998,2000,2001, 2002, 2003, 2004, 2006, 2008, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, Inc. +/* Copyright (C) 1995,1996,1997,1998,2000,2001, 2002, 2003, 2004, 2006, 2008, 2009, 2010, 2011, 2012, 2013, 2014 Free Software Foundation, Inc. * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public License @@ -52,6 +52,7 @@ extern "C" { #include "libguile/finalizers.h" #include "libguile/fluids.h" #include "libguile/foreign.h" +#include "libguile/foreign-object.h" #include "libguile/fports.h" #include "libguile/gc.h" #include "libguile/generalized-arrays.h" diff --git a/libguile/Makefile.am b/libguile/Makefile.am index f5e859023..df0c7ce01 100644 --- a/libguile/Makefile.am +++ b/libguile/Makefile.am @@ -148,6 +148,7 @@ libguile_@GUILE_EFFECTIVE_VERSION@_la_SOURCES = \ finalizers.c \ fluids.c \ foreign.c \ + foreign-object.c \ fports.c \ frames.c \ gc-malloc.c \ @@ -587,6 +588,7 @@ modinclude_HEADERS = \ filesys.h \ fluids.h \ foreign.h \ + foreign-object.h \ fports.h \ frames.h \ gc.h \ diff --git a/libguile/foreign-object.c b/libguile/foreign-object.c new file mode 100644 index 000000000..830f73f80 --- /dev/null +++ b/libguile/foreign-object.c @@ -0,0 +1,229 @@ +/* Copyright (C) 2014 Free Software Foundation, Inc. + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public License + * as published by the Free Software Foundation; either version 3 of + * the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA + * 02110-1301 USA + */ + + + +#ifdef HAVE_CONFIG_H +# include <config.h> +#endif + +#include "libguile/_scm.h" +#include "libguile/goops.h" +#include "libguile/foreign-object.h" + + + + +static SCM make_fobj_type_var; + +static void +init_make_fobj_type_var (void) +{ + make_fobj_type_var = scm_c_private_lookup ("system foreign-object", + "make-foreign-object-type"); +} + +SCM +scm_make_foreign_object_type (SCM name, SCM slot_names, + scm_t_struct_finalize finalizer) +{ + SCM type; + + static scm_i_pthread_once_t once = SCM_I_PTHREAD_ONCE_INIT; + scm_i_pthread_once (&once, init_make_fobj_type_var); + + type = scm_call_2 (scm_variable_ref (make_fobj_type_var), name, slot_names); + + if (finalizer) + SCM_SET_VTABLE_INSTANCE_FINALIZER (type, finalizer); + + return type; +} + +void +scm_assert_foreign_object_type (SCM type, SCM val) +{ + if (!SCM_IS_A_P (val, type)) + scm_error (scm_arg_type_key, NULL, "Wrong type (expecting ~A): ~S", + scm_list_2 (scm_class_name (type), val), scm_list_1 (val)); +} + +SCM +scm_make_foreign_object_0 (SCM type) +{ + return scm_make_foreign_object_n (type, 0, NULL); +} + +SCM +scm_make_foreign_object_1 (SCM type, void *val0) +{ + return scm_make_foreign_object_n (type, 1, &val0); +} + +SCM +scm_make_foreign_object_2 (SCM type, void *val0, void *val1) +{ + void *vals[2]; + + vals[0] = val0; + vals[1] = val1; + + return scm_make_foreign_object_n (type, 2, vals); +} + +SCM +scm_make_foreign_object_3 (SCM type, void *val0, void *val1, void *val2) +{ + void *vals[3]; + + vals[0] = val0; + vals[1] = val1; + vals[2] = val2; + + return scm_make_foreign_object_n (type, 3, vals); +} + +SCM +scm_make_foreign_object_n (SCM type, size_t n, void *vals[]) +#define FUNC_NAME "make-foreign-object" +{ + SCM obj; + SCM layout; + size_t i; + const char *layout_chars; + + SCM_VALIDATE_VTABLE (SCM_ARG1, type); + + layout = SCM_VTABLE_LAYOUT (type); + + if (scm_i_symbol_length (layout) / 2 < n) + scm_out_of_range (FUNC_NAME, scm_from_size_t (n)); + + layout_chars = scm_i_symbol_chars (layout); + for (i = 0; i < n; i++) + if (layout_chars[i * 2] != 'u') + scm_wrong_type_arg_msg (FUNC_NAME, 0, layout, "'u' field"); + + obj = scm_c_make_structv (type, 0, 0, NULL); + + for (i = 0; i < n; i++) + SCM_STRUCT_DATA_SET (obj, i, (scm_t_bits) vals[i]); + + return obj; +} +#undef FUNC_NAME + +scm_t_bits +scm_foreign_object_unsigned_ref (SCM obj, size_t n) +#define FUNC_NAME "foreign-object-ref" +{ + SCM layout; + + SCM_VALIDATE_STRUCT (SCM_ARG1, obj); + + layout = SCM_STRUCT_LAYOUT (obj); + if (scm_i_symbol_length (layout) / 2 < n) + scm_out_of_range (FUNC_NAME, scm_from_size_t (n)); + + if (scm_i_symbol_ref (layout, n * 2) != 'u') + scm_wrong_type_arg_msg (FUNC_NAME, 0, layout, "'u' field"); + + return SCM_STRUCT_DATA_REF (obj, n); +} +#undef FUNC_NAME + +void +scm_foreign_object_unsigned_set_x (SCM obj, size_t n, scm_t_bits val) +#define FUNC_NAME "foreign-object-set!" +{ + SCM layout; + + SCM_VALIDATE_STRUCT (SCM_ARG1, obj); + + layout = SCM_STRUCT_LAYOUT (obj); + if (scm_i_symbol_length (layout) / 2 < n) + scm_out_of_range (FUNC_NAME, scm_from_size_t (n)); + + if (scm_i_symbol_ref (layout, n * 2) != 'u') + scm_wrong_type_arg_msg (FUNC_NAME, 0, layout, "'u' field"); + + SCM_STRUCT_DATA_SET (obj, n, val); +} +#undef FUNC_NAME + +scm_t_signed_bits +scm_foreign_object_signed_ref (SCM obj, size_t n) +{ + scm_t_bits bits = scm_foreign_object_unsigned_ref (obj, n); + return (scm_t_signed_bits) bits; +} + +void +scm_foreign_object_signed_set_x (SCM obj, size_t n, scm_t_signed_bits val) +{ + scm_t_bits bits = (scm_t_bits) val; + scm_foreign_object_unsigned_set_x (obj, n, bits); +} + +void* +scm_foreign_object_ref (SCM obj, size_t n) +{ + scm_t_bits bits = scm_foreign_object_unsigned_ref (obj, n); + return (void *) bits; +} + +void +scm_foreign_object_set_x (SCM obj, size_t n, void *val) +{ + scm_t_bits bits = (scm_t_bits) val; + scm_foreign_object_unsigned_set_x (obj, n, bits); +} + +static void +invoke_finalizer (void *obj, void *data) +{ + scm_call_1 (PTR2SCM (data), PTR2SCM (obj)); +} + +static SCM +sys_add_finalizer_x (SCM obj, SCM finalizer) +#define FUNC_NAME "%add-finalizer!" +{ + SCM_VALIDATE_PROC (SCM_ARG2, finalizer); + + scm_i_add_finalizer (SCM2PTR (obj), invoke_finalizer, SCM2PTR (finalizer)); + + return SCM_UNSPECIFIED; +} +#undef FUNC_NAME + +static void +scm_init_foreign_object (void) +{ + scm_c_define_gsubr ("%add-finalizer!", 2, 0, 0, + (scm_t_subr) sys_add_finalizer_x); +} + +void +scm_register_foreign_object (void) +{ + scm_c_register_extension ("libguile-" SCM_EFFECTIVE_VERSION, + "scm_init_foreign_object", + (scm_t_extension_init_func)scm_init_foreign_object, + NULL); +} diff --git a/libguile/foreign-object.h b/libguile/foreign-object.h new file mode 100644 index 000000000..806b7eddb --- /dev/null +++ b/libguile/foreign-object.h @@ -0,0 +1,62 @@ +#ifndef SCM_FOREIGN_OBJECT_H +#define SCM_FOREIGN_OBJECT_H + +/* Copyright (C) 2014 Free Software Foundation, Inc. + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public License + * as published by the Free Software Foundation; either version 3 of + * the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA + * 02110-1301 USA + */ + + + +#include "libguile/__scm.h" +#include "libguile/print.h" + + + + +SCM_API SCM scm_make_foreign_object_type (SCM name, SCM slot_names, + scm_t_struct_finalize finalizer); + +SCM_API void scm_assert_foreign_object_type (SCM type, SCM val); + +/* All objects of a given foreign object type have the same number of + fields. When constructing a foreign object, you don't have to pass + initializers for all of the fields; it is always OK to call + scm_make_foreign_object_0 and initialize the fields by hand with + scm_foreign_object_set_x or other setters. The initial value of + fields that haven't been explicitly given a value is 0. */ +SCM_API SCM scm_make_foreign_object_0 (SCM type); +SCM_API SCM scm_make_foreign_object_1 (SCM type, void *val0); +SCM_API SCM scm_make_foreign_object_2 (SCM type, void *val0, void *val1); +SCM_API SCM scm_make_foreign_object_3 (SCM type, void *val0, void *val1, + void *val2); +SCM_API SCM scm_make_foreign_object_n (SCM type, size_t n, void *vals[]); + +SCM_API void* scm_foreign_object_ref (SCM obj, size_t n); +SCM_API void scm_foreign_object_set_x (SCM obj, size_t n, void *val); + +SCM_API scm_t_bits scm_foreign_object_unsigned_ref (SCM obj, size_t n); +SCM_API void scm_foreign_object_unsigned_set_x (SCM obj, size_t n, + scm_t_bits val); + +SCM_API scm_t_signed_bits scm_foreign_object_signed_ref (SCM obj, size_t n); +SCM_API void scm_foreign_object_signed_set_x (SCM obj, size_t n, + scm_t_signed_bits val); + +SCM_INTERNAL void scm_register_foreign_object (void); + + +#endif /* SCM_FOREIGN_OBJECT_H */ diff --git a/libguile/goops.c b/libguile/goops.c index 2cf343f79..450ae0d55 100644 --- a/libguile/goops.c +++ b/libguile/goops.c @@ -640,7 +640,7 @@ SCM_DEFINE (scm_sys_initialize_object, "%initialize-object", 2, 0, 0, get_n_set = SCM_CDR (get_n_set), slots = SCM_CDR (slots)) { SCM slot_name = SCM_CAR (slots); - SCM slot_value = SCM_PACK (0); + SCM slot_value = SCM_GOOPS_UNBOUND; if (!scm_is_null (SCM_CDR (slot_name))) { @@ -664,12 +664,12 @@ SCM_DEFINE (scm_sys_initialize_object, "%initialize-object", 2, 0, 0, slot_value = scm_i_get_keyword (tmp, initargs, n_initargs, - SCM_PACK (0), + SCM_GOOPS_UNBOUND, FUNC_NAME); } } - if (SCM_UNPACK (slot_value)) + if (!SCM_GOOPS_UNBOUNDP (slot_value)) /* set slot to provided value */ set_slot_value (class, obj, SCM_CAR (get_n_set), slot_value); else @@ -677,14 +677,10 @@ SCM_DEFINE (scm_sys_initialize_object, "%initialize-object", 2, 0, 0, /* set slot to its :init-form if it exists */ tmp = SCM_CADAR (get_n_set); if (scm_is_true (tmp)) - { - slot_value = get_slot_value (class, obj, SCM_CAR (get_n_set)); - if (SCM_GOOPS_UNBOUNDP (slot_value)) - set_slot_value (class, - obj, - SCM_CAR (get_n_set), - scm_call_0 (tmp)); - } + set_slot_value (class, + obj, + SCM_CAR (get_n_set), + scm_call_0 (tmp)); } } diff --git a/libguile/init.c b/libguile/init.c index 6de7a2192..b4c966caa 100644 --- a/libguile/init.c +++ b/libguile/init.c @@ -395,6 +395,7 @@ scm_i_init_guile (void *base) scm_bootstrap_vm (); scm_register_r6rs_ports (); scm_register_foreign (); + scm_register_foreign_object (); scm_register_srfi_1 (); scm_register_srfi_60 (); scm_register_poll (); diff --git a/module/Makefile.am b/module/Makefile.am index abc8a7363..7af35ed8f 100644 --- a/module/Makefile.am +++ b/module/Makefile.am @@ -381,6 +381,7 @@ SYSTEM_SOURCES = \ system/vm/disassembler.scm \ system/vm/vm.scm \ system/foreign.scm \ + system/foreign-object.scm \ system/xref.scm \ system/repl/debug.scm \ system/repl/error-handling.scm \ diff --git a/module/system/foreign-object.scm b/module/system/foreign-object.scm new file mode 100644 index 000000000..319b0f4e4 --- /dev/null +++ b/module/system/foreign-object.scm @@ -0,0 +1,88 @@ +;;; Wrapping foreign objects in Scheme + +;;; Copyright (C) 2014 Free Software Foundation, Inc. +;;; +;;; This library is free software; you can redistribute it and/or +;;; modify it under the terms of the GNU Lesser General Public +;;; License as published by the Free Software Foundation; either +;;; version 3 of the License, or (at your option) any later version. +;;; +;;; This library is distributed in the hope that it will be useful, +;;; but WITHOUT ANY WARRANTY; without even the implied warranty of +;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +;;; Lesser General Public License for more details. +;;; +;;; You should have received a copy of the GNU Lesser General Public +;;; License along with this library; if not, write to the Free Software +;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA +;;; + +;;; Commentary: +;; +;; +;;; Code: + +(define-module (system foreign-object) + #:use-module (oop goops) + #:export (make-foreign-object-type + define-foreign-object-type)) + +(eval-when (eval load expand) + (load-extension (string-append "libguile-" (effective-version)) + "scm_init_foreign_object")) + +(define-class <finalizer-class> (<class>) + (finalizer #:init-keyword #:finalizer #:init-value #f + #:getter finalizer)) + +(define-method (allocate-instance (class <finalizer-class>) initargs) + (let ((instance (next-method)) + (finalizer (finalizer class))) + (when finalizer + (%add-finalizer! instance finalizer)) + instance)) + +(define (getter-method class slot-name existing) + (let ((getter (ensure-generic existing slot-name)) + (slot-def (or (assq slot-name (slot-ref class 'getters-n-setters)) + (slot-missing class slot-name)))) + (add-method! getter (compute-getter-method class slot-def)) + getter)) + +(define* (make-foreign-object-type name slots #:key finalizer) + (unless (symbol? name) + (error "type name should be a symbol" name)) + (unless (or (not finalizer) (procedure? finalizer)) + (error "finalizer should be a procedure" finalizer)) + (let ((dslots (map (lambda (slot) + (unless (symbol? slot) + (error "slot name should be a symbol" slot)) + (list slot #:class <foreign-slot> + #:init-keyword (symbol->keyword slot) + #:init-value 0)) + slots))) + (if finalizer + (make-class '() dslots #:name name + #:finalizer finalizer #:metaclass <finalizer-class>) + (make-class '() dslots #:name name)))) + +(define-syntax define-foreign-object-type + (lambda (x) + (define (kw-apply slots) + (syntax-case slots () + (() #'()) + ((slot . slots) + (let ((kw (symbol->keyword (syntax->datum #'slot)))) + #`(#,kw slot . #,(kw-apply #'slots)))))) + + (syntax-case x () + ((_ name constructor (slot ...) kwarg ...) + #`(begin + (define name + (make-foreign-object-type 'name '(slot ...) kwarg ...)) + (define slot + (getter-method name 'slot (and (defined? 'slot) slot))) + ... + (define constructor + (lambda (slot ...) + (make name #,@(kw-apply #'(slot ...)))))))))) diff --git a/test-suite/standalone/Makefile.am b/test-suite/standalone/Makefile.am index fa77925d9..ce5f36959 100644 --- a/test-suite/standalone/Makefile.am +++ b/test-suite/standalone/Makefile.am @@ -129,6 +129,17 @@ TESTS += test-ffi endif HAVE_SHARED_LIBRARIES +# test-foreign-object-scm +check_SCRIPTS += test-foreign-object-scm +TESTS += test-foreign-object-scm + +# test-foreign-object-c +test_foreign_object_c_SOURCES = test-foreign-object-c.c +test_foreign_object_c_CFLAGS = ${test_cflags} +test_foreign_object_c_LDADD = $(LIBGUILE_LDADD) +check_PROGRAMS += test-foreign-object-c +TESTS += test-foreign-object-c + # test-list test_list_SOURCES = test-list.c test_list_CFLAGS = ${test_cflags} diff --git a/test-suite/standalone/test-foreign-object-c.c b/test-suite/standalone/test-foreign-object-c.c new file mode 100644 index 000000000..613c1f631 --- /dev/null +++ b/test-suite/standalone/test-foreign-object-c.c @@ -0,0 +1,115 @@ +/* test-foreign-object-c.c - exercise C foreign object interface */ + +/* Copyright (C) 2014 Free Software Foundation, Inc. + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public License + * as published by the Free Software Foundation; either version 3 of + * the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA + * 02110-1301 USA + */ + +#ifdef HAVE_CONFIG_H +# include <config.h> +#endif + +#include <libguile.h> + +#include <stdlib.h> +#include <stdio.h> +#include <string.h> + +enum + { + CSTR_SLOT_ADDR, + CSTR_SLOT_LEN, + CSTR_SLOT_COUNT + }; + +static void +finalizer (SCM obj) +{ + free (scm_foreign_object_ref (obj, CSTR_SLOT_ADDR)); +} + +static SCM +make_cstr_from_static (SCM type, const char *str) +{ + char *ours = strdup (str); + + if (!ours) + abort (); + + return scm_make_foreign_object_2 (type, ours, (void *) strlen (ours)); +} + +static int +cstr_equals_static_p (SCM cstr, const char *str) +{ + const char *addr; + size_t len; + + addr = scm_foreign_object_ref (cstr, CSTR_SLOT_ADDR); + len = scm_foreign_object_unsigned_ref (cstr, CSTR_SLOT_LEN); + + if (strlen (str) != len) + return 0; + + return strncmp (addr, str, len) == 0; +} + +static void +test_scm_foreign_object (void) +{ + SCM type_name, slot_names, type, cstr; + + type_name = scm_from_utf8_symbol ("<cstr>"); + slot_names = scm_list_2 (scm_from_utf8_symbol ("addr"), + scm_from_utf8_symbol ("len")); + type = scm_make_foreign_object_type (type_name, slot_names, finalizer); + + cstr = make_cstr_from_static (type, "Hello, world!"); + scm_assert_foreign_object_type (type, cstr); + + if (!cstr_equals_static_p (cstr, "Hello, world!")) + { + fprintf (stderr, "fail: test-foreign-object 1\n"); + exit (EXIT_FAILURE); + } + + { + int i; + for (i = 0; i < 5000; i++) + cstr = make_cstr_from_static (type, "Hello, world!"); + cstr = SCM_BOOL_F; + } + + scm_gc (); + scm_gc (); + scm_gc (); + + /* Allow time for the finalizer thread to run. */ + scm_usleep (scm_from_uint (50 * 1000)); +} + +static void +tests (void *data, int argc, char **argv) +{ + test_scm_foreign_object (); +} + +int +main (int argc, char *argv[]) +{ + scm_boot_guile (argc, argv, tests, NULL); + return 0; +} diff --git a/test-suite/standalone/test-foreign-object-scm b/test-suite/standalone/test-foreign-object-scm new file mode 100755 index 000000000..7e4bd85d8 --- /dev/null +++ b/test-suite/standalone/test-foreign-object-scm @@ -0,0 +1,119 @@ +#!/bin/sh +exec guile -q -s "$0" "$@" +!# +;;; test-foreign-object-scm --- Foreign object interface. -*- Scheme -*- +;;; +;;; Copyright (C) 2014 Free Software Foundation, Inc. +;;; +;;; This library is free software; you can redistribute it and/or +;;; modify it under the terms of the GNU Lesser General Public +;;; License as published by the Free Software Foundation; either +;;; version 3 of the License, or (at your option) any later version. +;;; +;;; This library is distributed in the hope that it will be useful, +;;; but WITHOUT ANY WARRANTY; without even the implied warranty of +;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +;;; Lesser General Public License for more details. +;;; +;;; You should have received a copy of the GNU Lesser General Public +;;; License along with this library; if not, write to the Free Software +;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + +(use-modules (system foreign) + (system foreign-object) + (rnrs bytevectors) + (oop goops)) + +(define (libc-ptr name) + (catch #t + (lambda () (dynamic-pointer name (dynamic-link))) + (lambda (k . args) + (print-exception (current-error-port) #f k args) + (write "Skipping test.\n" (current-error-port)) + (exit 0)))) + +(define malloc (pointer->procedure '* (libc-ptr "malloc") (list size_t))) +(define memcpy (pointer->procedure void (libc-ptr "memcpy") (list '* '* size_t))) +(define free (pointer->procedure void (libc-ptr "free") '(*))) + +(define (finalize-cstr cstr) + (free (make-pointer (addr cstr)))) + +(define-foreign-object-type <cstr> make-cstr (addr len) + #:finalizer finalize-cstr) + +(define (cstr->string cstr) + (pointer->string (make-pointer (addr cstr)) (len cstr) "UTF-8")) + +(define* (string->cstr str #:optional (k make-cstr)) + (let* ((bv (string->utf8 str)) + (len (bytevector-length bv)) + (mem (malloc len))) + (when (null-pointer? mem) + (error "Out of memory.")) + (memcpy mem (bytevector->pointer bv) len) + (k (pointer-address mem) len))) + +(define-method (write (cstr <cstr>) port) + (format port "<<cstr> ~s>" (cstr->string cstr))) + +(define-method (display (cstr <cstr>) port) + (display (cstr->string cstr) port)) + +(define-method (+ (a <cstr>) (b <cstr>)) + (string->cstr (string-append (cstr->string a) (cstr->string b)))) + +(define-method (equal? (a <cstr>) (b <cstr>)) + (equal? (cstr->string a) (cstr->string b))) + +(define failed? #f) +(define-syntax test + (syntax-rules () + ((_ exp res) + (let ((expected res) + (actual exp)) + (if (not (equal? actual expected)) + (begin + (set! failed? #t) + (format (current-error-port) + "bad return from expression `~a': expected ~A; got ~A~%" + 'exp expected actual))))))) + +(test (string->cstr "Hello, world!") + (+ (string->cstr "Hello, ") (string->cstr "world!"))) + +;; GOOPS construction syntax instead of make-cstr. +(test (string->cstr "Hello, world!") + (string->cstr "Hello, world!" + (lambda (addr len) + (make <cstr> #:addr addr #:len len)))) + +;; Subclassing. +(define-class <wrapped-cstr> (<cstr>) + (wrapped-string #:init-keyword #:wrapped-string + #:getter wrapped-string + #:init-form (error "missing #:wrapped-string"))) + +(define (string->wrapped-cstr string) + (string->cstr string (lambda (addr len) + (make <wrapped-cstr> #:addr addr #:len len + #:wrapped-string string)))) + +(let ((wrapped-cstr (string->wrapped-cstr "Hello, world!"))) + ;; Tests that <cst> methods work on <wrapped-cstr>. + (test "Hello, world!" (cstr->string wrapped-cstr)) + ;; Test the additional #:wrapped-string slot. + (test "Hello, world!" (wrapped-string wrapped-cstr))) + +(gc) (gc) (gc) + +;; Sleep 50 milliseconds to allow the finalization thread to run. +(usleep #e50e3) + +;; But we don't really know if it ran. Oh well. + +(exit (if failed? 1 0)) + +;; Local Variables: +;; mode: scheme +;; End: diff --git a/test-suite/tests/goops.test b/test-suite/tests/goops.test index 1705ee811..d8a5ecfad 100644 --- a/test-suite/tests/goops.test +++ b/test-suite/tests/goops.test @@ -1,6 +1,6 @@ ;;;; goops.test --- test suite for GOOPS -*- scheme -*- ;;;; -;;;; Copyright (C) 2001,2003,2004, 2006, 2008, 2009, 2011, 2012 Free Software Foundation, Inc. +;;;; Copyright (C) 2001,2003,2004, 2006, 2008, 2009, 2011, 2012, 2014 Free Software Foundation, Inc. ;;;; ;;;; This library is free software; you can redistribute it and/or ;;;; modify it under the terms of the GNU Lesser General Public @@ -474,9 +474,9 @@ (x bar) (set! (x bar) 2) (equal? (reverse z) - '(before-ref before-set! 1 before-ref after-ref - after-set! 1 1 before-ref after-ref - before-set! 2 before-ref after-ref after-set! 2 2))) + '(before-set! 1 before-ref after-ref + after-set! 1 1 before-ref after-ref + before-set! 2 before-ref after-ref after-set! 2 2))) (current-module)))) (use-modules (oop goops composite-slot)) @@ -527,3 +527,38 @@ exception:no-applicable-method (eval '(quxy 1) (current-module)))) + +(with-test-prefix "foreign slots" + (define-class <foreign-test> () + (a #:init-keyword #:a #:class <foreign-slot> + #:accessor test-a) + (b #:init-keyword #:b #:init-form 3 #:class <foreign-slot> + #:accessor test-b)) + + (pass-if-equal "constructing, no initargs" + '(0 3) + (let ((x (make <foreign-test>))) + (list (slot-ref x 'a) + (slot-ref x 'b)))) + + (pass-if-equal "constructing, initargs" + '(1 2) + (let ((x (make <foreign-test> #:a 1 #:b 2))) + (list (slot-ref x 'a) + (slot-ref x 'b)))) + + (pass-if-equal "getters" + '(0 3) + (let ((x (make <foreign-test>))) + (list (test-a x) (test-b x)))) + + (pass-if-equal "setters" + '(10 20) + (let ((x (make <foreign-test>))) + (set! (test-a x) 10) + (set! (test-b x) 20) + (list (test-a x) (test-b x)))) + + (pass-if-exception "out of range" + exception:out-of-range + (make <foreign-test> #:a (ash 1 64)))) |