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, 11 insertions, 9 deletions

diff --git a/src/lisp.h b/src/lisp.h
index 53bfd7c4daf..15c459c9fdb 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -4451,12 +4451,6 @@ egetenv (const char *var)
   return egetenv_internal (var, strlen (var));
 }
 
-/* Copy Lisp string to temporary (allocated on stack) C string.  */
-
-#define xlispstrdupa(string)                    \
-  memcpy (alloca (SBYTES (string) + 1),         \
-          SSDATA (string), SBYTES (string) + 1)
-
 /* Set up the name of the machine we're running on.  */
 extern void init_system_name (void);
 
@@ -4484,7 +4478,7 @@ extern void *record_xmalloc (size_t) ATTRIBUTE_ALLOC_SIZE ((1));
 
 /* SAFE_ALLOCA allocates a simple buffer.  */
 
-#define SAFE_ALLOCA(size) ((size) < MAX_ALLOCA  \
+#define SAFE_ALLOCA(size) ((size) <= MAX_ALLOCA \
                            ? alloca (size)      \
                            : (sa_must_free = true, record_xmalloc (size)))
 
@@ -4504,6 +4498,14 @@ extern void *record_xmalloc (size_t) ATTRIBUTE_ALLOC_SIZE ((1));
       }                                                          \
   } while (false)
 
+/* SAFE_ALLOCA_STRING allocates a C copy of a Lisp string.  */
+
+#define SAFE_ALLOCA_STRING(ptr, string)                 \
+  do {                                                  \
+    (ptr) = SAFE_ALLOCA (SBYTES (string) + 1);          \
+    memcpy (ptr, SDATA (string), SBYTES (string) + 1);  \
+  } while (false)
+
 /* SAFE_FREE frees xmalloced memory and enables GC as needed.  */
 
 #define SAFE_FREE()                     \
@@ -4519,9 +4521,9 @@ extern void *record_xmalloc (size_t) ATTRIBUTE_ALLOC_SIZE ((1));
 
 #define SAFE_ALLOCA_LISP(buf, nelt)                            \
   do {                                                         \
-    if ((nelt) < MAX_ALLOCA / word_size)                       \
+    if ((nelt) <= MAX_ALLOCA / word_size)                      \
       (buf) = alloca ((nelt) * word_size);                     \
-    else if ((nelt) < min (PTRDIFF_MAX, SIZE_MAX) / word_size) \
+    else if ((nelt) <= min (PTRDIFF_MAX, SIZE_MAX) / word_size) \
       {                                                        \
         Lisp_Object arg_;                                      \
         (buf) = xmalloc ((nelt) * word_size);                  \