Use SAFE_ALLOCA etc. to avoid unbounded stack allocation.

This follows up on the recent thread in emacs-devel on alloca; see:
http://lists.gnu.org/archive/html/emacs-devel/2014-09/msg00042.html
This patch also cleans up alloca-related glitches noted while
examining the code looking for unbounded alloca.
* alloc.c (listn):
* callproc.c (init_callproc):
Rewrite to avoid need for alloca.
* buffer.c (mouse_face_overlay_overlaps)
(report_overlay_modification):
* buffer.h (GET_OVERLAYS_AT):
* coding.c (make_subsidiaries):
* doc.c (Fsnarf_documentation):
* editfns.c (Fuser_full_name):
* fileio.c (Ffile_name_directory, Fexpand_file_name)
(search_embedded_absfilename, Fsubstitute_in_file_name):
* fns.c (Fmake_hash_table):
* font.c (font_vconcat_entity_vectors, font_update_drivers):
* fontset.c (fontset_pattern_regexp, Ffontset_info):
* frame.c (Fmake_terminal_frame, x_set_frame_parameters)
(xrdb_get_resource, x_get_resource_string):
* ftfont.c (ftfont_get_charset, ftfont_check_otf, ftfont_drive_otf):
* ftxfont.c (ftxfont_draw):
* image.c (xbm_load, xpm_load, jpeg_load_body):
* keyboard.c (echo_add_key, menu_bar_items, tool_bar_items):
* keymap.c (Fdescribe_buffer_bindings, describe_map):
* lread.c (openp):
* menu.c (digest_single_submenu, find_and_call_menu_selection)
(find_and_return_menu_selection):
* print.c (PRINTFINISH):
* process.c (Fformat_network_address):
* scroll.c (do_scrolling, do_direct_scrolling, scrolling_1):
* search.c (search_buffer, Fmatch_data, Fregexp_quote):
* sound.c (wav_play, au_play):
* syntax.c (skip_chars):
* term.c (tty_menu_activate, tty_menu_show):
* textprop.c (get_char_property_and_overlay):
* window.c (Fset_window_configuration):
* xdisp.c (safe__call, next_overlay_change, vmessage)
(compute_overhangs_and_x, draw_glyphs, note_mouse_highlight):
* xfaces.c (face_at_buffer_position):
* xmenu.c (x_menu_show):
Use SAFE_ALLOCA etc. instead of plain alloca, since the
allocation size isn't bounded.
* callint.c (Fcall_interactively): Redo memory_full check
so that it can be done at compile-time on some platforms.
* coding.c (MAX_LOOKUP_MAX): New constant.
(get_translation_table): Use it.
* callproc.c (call_process): Use SAFE_NALLOCA instead of
SAFE_ALLOCA, to catch integer overflows on size calculation.
(exec_failed) [!DOS_NT]: New function.
(child_setup) [!DOS_NT]: Use it.
* editfns.c (Ftranspose_regions):
Hoist USE_SAFE_ALLOC + SAFE_FREE out of 'if'.
* editfns.c (check_translation):
Allocate larger buffers on the heap.
* eval.c (internal_lisp_condition_case):
Check for MAX_ALLOCA overflow.
* fns.c (sort_vector): Use SAFE_ALLOCA_LISP rather than Fmake_vector.
(Fbase64_encode_region, Fbase64_decode_region):
Avoid unnecessary calls to SAFE_FREE before 'error'.
* buffer.c (mouse_face_overlay_overlaps):
* editfns.c (Fget_pos_property, check_translation):
* eval.c (Ffuncall):
* font.c (font_unparse_xlfd, font_find_for_lface):
* ftfont.c (ftfont_drive_otf):
* keyboard.c (echo_add_key, read_decoded_event_from_main_queue)
(menu_bar_items, tool_bar_items):
* sound.c (Fplay_sound_internal):
* xdisp.c (load_overlay_strings, dump_glyph_row):
Use an ordinary auto buffer rather than alloca, since the
allocation size is fixed and small.
* ftfont.c: Include <c-strcase.h>.
(matching_prefix): New function.
(get_adstyle_property): Use it, to avoid need for alloca.
* keyboard.c (echo_add_key):
* keymap.c (describe_map): Use ptrdiff_t, not int.
* keyboard.c (echo_add_key): Prefer sizeof to strlen.
* keymap.c (Fdescribe_buffer_bindings): Use SBYTES, not SCHARS,
when counting bytes.
* lisp.h (xlispstrdupa): Remove, replacing with ...
(SAFE_ALLOCA_STRING): ... new macro with different API.
This fixes a portability problem, namely, alloca result
passed to another function.  All uses changed.
(SAFE_ALLOCA, SAFE_ALLOCA_LISP): Check for MAX_ALLOCA,
not MAX_ALLOCA - 1.
* regex.c (REGEX_USE_SAFE_ALLOCA, REGEX_SAFE_FREE)
(REGEX_ALLOCATE): New macros.
(REGEX_REALLOCATE, REGEX_ALLOCATE_STACK, REGEX_REALLOCATE_STACK)
(REGEX_FREE_STACK, FREE_VARIABLES, re_match_2_internal):
Use them.
* xdisp.c (message3): Use SAFE_ALLOCA_STRING rather than doing it
by hand.
(decode_mode_spec_coding): Store directly into buf rather than
into an alloca temporary and copying the temporary to the buf.

Fixes: debbugs:18410

1 files changed, 30 insertions, 24 deletions

diff --git a/src/editfns.c b/src/editfns.c
index a906aead09a..7e9a3bf7d3c 100644
--- a/src/editfns.c
+++ b/src/editfns.c
@@ -376,13 +376,14 @@ at POSITION.  */)
       set_buffer_temp (XBUFFER (object));
 
       /* First try with room for 40 overlays.  */
-      noverlays = 40;
-      overlay_vec = alloca (noverlays * sizeof *overlay_vec);
+      Lisp_Object overlay_vecbuf[40];
+      noverlays = ARRAYELTS (overlay_vecbuf);
+      overlay_vec = overlay_vecbuf;
       noverlays = overlays_around (posn, overlay_vec, noverlays);
 
       /* If there are more than 40,
 	 make enough space for all, and try again.  */
-      if (noverlays > 40)
+      if (ARRAYELTS (overlay_vecbuf) < noverlays)
 	{
 	  SAFE_ALLOCA_LISP (overlay_vec, noverlays);
 	  noverlays = overlays_around (posn, overlay_vec, noverlays);
@@ -1325,17 +1326,16 @@ name, or nil if there is no such user.  */)
   /* Substitute the login name for the &, upcasing the first character.  */
   if (q)
     {
-      register char *r;
-      Lisp_Object login;
-
-      login = Fuser_login_name (make_number (pw->pw_uid));
-      r = alloca (strlen (p) + SCHARS (login) + 1);
+      Lisp_Object login = Fuser_login_name (make_number (pw->pw_uid));
+      USE_SAFE_ALLOCA;
+      char *r = SAFE_ALLOCA (strlen (p) + SBYTES (login) + 1);
       memcpy (r, p, q - p);
       r[q - p] = 0;
       strcat (r, SSDATA (login));
       r[q - p] = upcase ((unsigned char) r[q - p]);
       strcat (r, q + 1);
       full = build_string (r);
+      SAFE_FREE ();
     }
 #endif /* AMPERSAND_FULL_NAME */
 
@@ -3012,8 +3012,12 @@ static Lisp_Object
 check_translation (ptrdiff_t pos, ptrdiff_t pos_byte, ptrdiff_t end,
 		   Lisp_Object val)
 {
-  int buf_size = 16, buf_used = 0;
-  int *buf = alloca (sizeof (int) * buf_size);
+  int initial_buf[16];
+  int *buf = initial_buf;
+  ptrdiff_t buf_size = ARRAYELTS (initial_buf);
+  int *bufalloc = 0;
+  ptrdiff_t buf_used = 0;
+  Lisp_Object result = Qnil;
 
   for (; CONSP (val); val = XCDR (val))
     {
@@ -3038,12 +3042,11 @@ check_translation (ptrdiff_t pos, ptrdiff_t pos_byte, ptrdiff_t end,
 
 		  if (buf_used == buf_size)
 		    {
-		      int *newbuf;
-
-		      buf_size += 16;
-		      newbuf = alloca (sizeof (int) * buf_size);
-		      memcpy (newbuf, buf, sizeof (int) * buf_used);
-		      buf = newbuf;
+		      bufalloc = xpalloc (bufalloc, &buf_size, 1, -1,
+					  sizeof *bufalloc);
+		      if (buf == initial_buf)
+			memcpy (bufalloc, buf, sizeof initial_buf);
+		      buf = bufalloc;
 		    }
 		  buf[buf_used++] = STRING_CHAR_AND_LENGTH (p, len1);
 		  pos_byte += len1;
@@ -3052,10 +3055,15 @@ check_translation (ptrdiff_t pos, ptrdiff_t pos_byte, ptrdiff_t end,
 		break;
 	    }
 	  if (i == len)
-	    return XCAR (val);
+	    {
+	      result = XCAR (val);
+	      break;
+	    }
 	}
     }
-  return Qnil;
+
+  xfree (bufalloc);
+  return result;
 }
 
 
@@ -4617,11 +4625,11 @@ Transposing beyond buffer boundaries is an error.  */)
       if (tmp_interval3)
 	set_text_properties_1 (startr1, endr2, Qnil, buf, tmp_interval3);
 
+      USE_SAFE_ALLOCA;
+
       /* First region smaller than second.  */
       if (len1_byte < len2_byte)
         {
-	  USE_SAFE_ALLOCA;
-
 	  temp = SAFE_ALLOCA (len2_byte);
 
 	  /* Don't precompute these addresses.  We have to compute them
@@ -4633,21 +4641,19 @@ Transposing beyond buffer boundaries is an error.  */)
           memcpy (temp, start2_addr, len2_byte);
           memcpy (start1_addr + len2_byte, start1_addr, len1_byte);
           memcpy (start1_addr, temp, len2_byte);
-	  SAFE_FREE ();
         }
       else
 	/* First region not smaller than second.  */
         {
-	  USE_SAFE_ALLOCA;
-
 	  temp = SAFE_ALLOCA (len1_byte);
 	  start1_addr = BYTE_POS_ADDR (start1_byte);
 	  start2_addr = BYTE_POS_ADDR (start2_byte);
           memcpy (temp, start1_addr, len1_byte);
           memcpy (start1_addr, start2_addr, len2_byte);
           memcpy (start1_addr + len2_byte, temp, len1_byte);
-	  SAFE_FREE ();
         }
+
+      SAFE_FREE ();
       graft_intervals_into_buffer (tmp_interval1, start1 + len2,
                                    len1, current_buffer, 0);
       graft_intervals_into_buffer (tmp_interval2, start1,