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, 18 insertions, 19 deletions

diff --git a/src/alloc.c b/src/alloc.c
index bb47a24d905..31b0644c285 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -2618,29 +2618,28 @@ list5 (Lisp_Object arg1, Lisp_Object arg2, Lisp_Object arg3, Lisp_Object arg4, L
 Lisp_Object
 listn (enum constype type, ptrdiff_t count, Lisp_Object arg, ...)
 {
-  va_list ap;
-  ptrdiff_t i;
-  Lisp_Object val, *objp;
+  Lisp_Object (*cons) (Lisp_Object, Lisp_Object);
+  switch (type)
+    {
+    case CONSTYPE_PURE: cons = pure_cons; break;
+    case CONSTYPE_HEAP: cons = Fcons; break;
+    default: emacs_abort ();
+    }
 
-  /* Change to SAFE_ALLOCA if you hit this eassert.  */
-  eassert (count <= MAX_ALLOCA / word_size);
+  eassume (0 < count);
+  Lisp_Object val = cons (arg, Qnil);
+  Lisp_Object tail = val;
 
-  objp = alloca (count * word_size);
-  objp[0] = arg;
+  va_list ap;
   va_start (ap, arg);
-  for (i = 1; i < count; i++)
-    objp[i] = va_arg (ap, Lisp_Object);
-  va_end (ap);
-
-  for (val = Qnil, i = count - 1; i >= 0; i--)
+  for (ptrdiff_t i = 1; i < count; i++)
     {
-      if (type == CONSTYPE_PURE)
-        val = pure_cons (objp[i], val);
-      else if (type == CONSTYPE_HEAP)
-        val = Fcons (objp[i], val);
-      else
-        emacs_abort ();
+      Lisp_Object elem = cons (va_arg (ap, Lisp_Object), Qnil);
+      XSETCDR (tail, elem);
+      tail = elem;
     }
+  va_end (ap);
+
   return val;
 }
 
@@ -3620,7 +3619,7 @@ make_save_int_obj (ptrdiff_t a, Lisp_Object b)
   p->data[1].object = b;
   return val;
 }
-  
+
 #if ! (defined USE_X_TOOLKIT || defined USE_GTK)
 Lisp_Object
 make_save_ptr_ptr (void *a, void *b)