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Avoid crashes in regex-emacs.c due to GC

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* src/regex-emacs.c (re_match_2_internal): Prevent GC from
invalidating C pointers to buffer text.  (Bug#40661)
This commit is contained in:
Eli Zaretskii 2020-04-18 14:53:13 +03:00
parent 175c61c18b
commit f3b62b6c62
1 changed files with 22 additions and 0 deletions
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22
src/regex-emacs.c
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@ -3853,6 +3853,12 @@ re_match_2 (struct re_pattern_buffer *bufp,
return result; return result;
} }
static void
unwind_re_match (void *ptr)
{
struct buffer *b = (struct buffer *) ptr;
b->text->inhibit_shrinking = 0;
}
/* This is a separate function so that we can force an alloca cleanup /* This is a separate function so that we can force an alloca cleanup
afterwards. */ afterwards. */
@ -3949,6 +3955,19 @@ re_match_2_internal (struct re_pattern_buffer *bufp,
INIT_FAIL_STACK (); INIT_FAIL_STACK ();
ptrdiff_t count = SPECPDL_INDEX ();
/* Prevent shrinking and relocation of buffer text if GC happens
while we are inside this function. The calls to
UPDATE_SYNTAX_TABLE_* macros can trigger GC if they call Lisp,
and we have C pointers to buffer text that must not become
invalid as result of GC. */
if (!current_buffer->text->inhibit_shrinking)
{
record_unwind_protect_ptr (unwind_re_match, current_buffer);
current_buffer->text->inhibit_shrinking = 1;
}
/* Do not bother to initialize all the register variables if there are /* Do not bother to initialize all the register variables if there are
no groups in the pattern, as it takes a fair amount of time. If no groups in the pattern, as it takes a fair amount of time. If
there are groups, we include space for register 0 (the whole there are groups, we include space for register 0 (the whole
@ -3965,6 +3984,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp,
/* The starting position is bogus. */ /* The starting position is bogus. */
if (pos < 0 || pos > size1 + size2) if (pos < 0 || pos > size1 + size2)
{ {
unbind_to (count, Qnil);
SAFE_FREE (); SAFE_FREE ();
return -1; return -1;
} }
@ -4179,6 +4199,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp,
DEBUG_PRINT ("Returning %td from re_match_2.\n", dcnt); DEBUG_PRINT ("Returning %td from re_match_2.\n", dcnt);
unbind_to (count, Qnil);
SAFE_FREE (); SAFE_FREE ();
return dcnt; return dcnt;
} }
@ -5025,6 +5046,7 @@ re_match_2_internal (struct re_pattern_buffer *bufp,
if (best_regs_set) if (best_regs_set)
goto restore_best_regs; goto restore_best_regs;
unbind_to (count, Qnil);
SAFE_FREE (); SAFE_FREE ();
return -1; /* Failure to match. */ return -1; /* Failure to match. */