Improve make-temp-file performance on local files

For the motivation behind this patch, please see Bug#28023 and:
http://emacshorrors.com/posts/make-temp-name.html
Although, given the recent changes to Tramp, the related security
problem in make-temp-file is already fixed, make-temp-file still has
several unnecessary system calls.  In the typical case on GNU/Linux,
this patch replaces 8 syscalls (symlink, open, close, readlinkat, uname,
getpid, unlink, umask) by 2 (open, close).
* admin/merge-gnulib (GNULIB_MODULES): Add tempname, now
that Emacs is using it directly.
* configure.ac (AUTO_DEPEND): Remove AC_SYS_LONG_FILE_NAMES;
no longer needed.
* lib/gnulib.mk.in, m4/gnulib-comp.m4: Regenerate.
* lisp/files.el (files--make-magic-temp-file): Rename from
make-temp-file.
(make-temp-file): Use make-temp-file-internal for
non-magic file names.
* src/fileio.c: Include tempname.h.
(make_temp_name_tbl, make_temp_name_count)
(make_temp_name_count_initialized_p, make_temp_name): Remove.
(Fmake_temp_file_internal): New function.
(Fmake_temp_name): Use it.
* src/filelock.c (get_boot_time): Use Fmake_temp_file_internal
instead of make_temp_name.

1 files changed, 9 insertions, 0 deletions

diff --git a/lisp/files.el b/lisp/files.el
index 0fe7f9c522a..19573cdf7b2 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -1407,6 +1407,15 @@ You can then use `write-region' to write new data into the file.
 If DIR-FLAG is non-nil, create a new empty directory instead of a file.
 
 If SUFFIX is non-nil, add that at the end of the file name."
+  (let ((absolute-prefix (expand-file-name prefix temporary-file-directory)))
+    (if (find-file-name-handler absolute-prefix 'write-region)
+        (files--make-magic-temp-file prefix dir-flag suffix)
+      (make-temp-file-internal absolute-prefix
+			       (if dir-flag t) (or suffix "")))))
+
+(defun files--make-magic-temp-file (prefix &optional dir-flag suffix)
+  "Implement (make-temp-file PREFIX DIR-FLAG SUFFIX).
+This implementation works on magic file names."
   ;; Create temp files with strict access rights.  It's easy to
   ;; loosen them later, whereas it's impossible to close the
   ;; time-window of loose permissions otherwise.