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, 20 insertions, 14 deletions

diff --git a/src/callint.c b/src/callint.c
index 817f84d897b..9a4573c77be 100644
--- a/src/callint.c
+++ b/src/callint.c
@@ -297,6 +297,7 @@ invoke it.  If KEYS is omitted or nil, the return value of
   Lisp_Object teml;
   Lisp_Object up_event;
   Lisp_Object enable;
+  USE_SAFE_ALLOCA;
   ptrdiff_t speccount = SPECPDL_INDEX ();
 
   /* The index of the next element of this_command_keys to examine for
@@ -366,12 +367,8 @@ invoke it.  If KEYS is omitted or nil, the return value of
       wrong_type_argument (Qcommandp, function);
   }
 
-  /* If SPECS is set to a string, use it as an interactive prompt.  */
-  if (STRINGP (specs))
-    /* Make a copy of string so that if a GC relocates specs,
-       `string' will still be valid.  */
-    string = xlispstrdupa (specs);
-  else
+  /* If SPECS is not a string, invent one.  */
+  if (! STRINGP (specs))
     {
       Lisp_Object input;
       Lisp_Object funval = Findirect_function (function, Qt);
@@ -416,10 +413,16 @@ invoke it.  If KEYS is omitted or nil, the return value of
         args[0] = Qfuncall_interactively;
         args[1] = function;
         args[2] = specs;
-        return unbind_to (speccount, Fapply (3, args));
+        Lisp_Object result = unbind_to (speccount, Fapply (3, args));
+        SAFE_FREE ();
+        return result;
       }
     }
 
+  /* SPECS is set to a string; use it as an interactive prompt.
+     Copy it so that STRING will be valid even if a GC relocates SPECS.  */
+  SAFE_ALLOCA_STRING (string, specs);
+
   /* Here if function specifies a string to control parsing the defaults.  */
 
   /* Set next_event to point to the first event with parameters.  */
@@ -507,14 +510,15 @@ invoke it.  If KEYS is omitted or nil, the return value of
         break;
     }
 
-  if (min (MOST_POSITIVE_FIXNUM,
-           min (PTRDIFF_MAX, SIZE_MAX) / word_size)
-      < nargs)
+  if (MOST_POSITIVE_FIXNUM < min (PTRDIFF_MAX, SIZE_MAX) / word_size
+      && MOST_POSITIVE_FIXNUM < nargs)
     memory_full (SIZE_MAX);
 
-  args = alloca (nargs * sizeof *args);
-  visargs = alloca (nargs * sizeof *visargs);
-  varies = alloca (nargs * sizeof *varies);
+  /* Allocate them all at one go.  This wastes a bit of memory, but
+     it's OK to trade space for speed.  */
+  SAFE_NALLOCA (args, 3, nargs);
+  visargs = args + nargs;
+  varies = (signed char *) (visargs + nargs);
 
   for (i = 0; i < nargs; i++)
     {
@@ -871,7 +875,9 @@ invoke it.  If KEYS is omitted or nil, the return value of
   {
     Lisp_Object val = Ffuncall (nargs, args);
     UNGCPRO;
-    return unbind_to (speccount, val);
+    val = unbind_to (speccount, val);
+    SAFE_FREE ();
+    return val;
   }
 }