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, 15 insertions, 6 deletions

diff --git a/src/doc.c b/src/doc.c
index df8cfba3f2a..be882d4a5c7 100644
--- a/src/doc.c
+++ b/src/doc.c
@@ -561,6 +561,8 @@ the same file name is found in the `doc-directory'.  */)
   char *p, *name;
   bool skip_file = 0;
   ptrdiff_t count;
+  char const *dirname;
+  ptrdiff_t dirlen;
   /* Preloaded defcustoms using custom-initialize-delay are added to
      this list, but kept unbound.  See http://debbugs.gnu.org/11565  */
   Lisp_Object delayed_init =
@@ -577,15 +579,21 @@ the same file name is found in the `doc-directory'.  */)
       (0)
 #endif /* CANNOT_DUMP */
     {
-      name = alloca (SCHARS (filename) + 14);
-      strcpy (name, "../etc/");
+      static char const sibling_etc[] = "../etc/";
+      dirname = sibling_etc;
+      dirlen = sizeof sibling_etc - 1;
     }
   else
     {
       CHECK_STRING (Vdoc_directory);
-      name = alloca (SCHARS (filename) + SCHARS (Vdoc_directory) + 1);
-      strcpy (name, SSDATA (Vdoc_directory));
+      dirname = SSDATA (Vdoc_directory);
+      dirlen = SBYTES (Vdoc_directory);
     }
+
+  count = SPECPDL_INDEX ();
+  USE_SAFE_ALLOCA;
+  name = SAFE_ALLOCA (dirlen + SBYTES (filename) + 1);
+  strcpy (name, dirname);
   strcat (name, SSDATA (filename));     /*** Add this line ***/
 
   /* Vbuild_files is nil when temacs is run, and non-nil after that.  */
@@ -608,7 +616,6 @@ the same file name is found in the `doc-directory'.  */)
       report_file_errno ("Opening doc string file", build_string (name),
                          open_errno);
     }
-  count = SPECPDL_INDEX ();
   record_unwind_protect_int (close_file_unwind, fd);
   Vdoc_file_name = filename;
   filled = 0;
@@ -637,7 +644,7 @@ the same file name is found in the `doc-directory'.  */)
                   && (end[-1] == 'o' || end[-1] == 'c'))
                 {
                   ptrdiff_t len = end - p - 2;
-                  char *fromfile = alloca (len + 1);
+                  char *fromfile = SAFE_ALLOCA (len + 1);
                   memcpy (fromfile, &p[2], len);
                   fromfile[len] = 0;
                   if (fromfile[len-1] == 'c')
@@ -688,6 +695,8 @@ the same file name is found in the `doc-directory'.  */)
       filled -= end - buf;
       memmove (buf, end, filled);
     }
+
+  SAFE_FREE ();
   return unbind_to (count, Qnil);
 }