Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx> writes:
> diff --git a/grep.c b/grep.c
> index 1157529115..49e9aed457 100644
> --- a/grep.c
> +++ b/grep.c
> @@ -351,6 +351,9 @@ static void compile_pcre1_regexp(struct grep_pat *p, const struct grep_opt *opt)
> const char *error;
> int erroffset;
> int options = PCRE_MULTILINE;
> +#ifdef PCRE_CONFIG_JIT
> + int canjit;
> +#endif
Is "canjit" a property purely of the library (e.g. version and
compilation option), or of combination of that and nature of the
pattern, or something else like the memory pressure?
I am wondering if it is worth doing something like this:
static int canjit = -1;
if (canjit < 0) {
pcre_config(PCRE_CONFIG_JIT, &canjit);
}
if it depends purely on the library linked to the process.
> @@ -365,9 +368,20 @@ static void compile_pcre1_regexp(struct grep_pat *p, const struct grep_opt *opt)
> if (!p->pcre1_regexp)
> compile_regexp_failed(p, error);
>
> - p->pcre1_extra_info = pcre_study(p->pcre1_regexp, 0, &error);
> + p->pcre1_extra_info = pcre_study(p->pcre1_regexp, PCRE_STUDY_JIT_COMPILE, &error);
> if (!p->pcre1_extra_info && error)
> die("%s", error);
> +
> +#ifdef PCRE_CONFIG_JIT
> + pcre_config(PCRE_CONFIG_JIT, &canjit);
> + if (canjit == 1) {
> + p->pcre1_jit_stack = pcre_jit_stack_alloc(1, 1024 * 1024);
> + if (!p->pcre1_jit_stack)
> + die("BUG: Couldn't allocate PCRE JIT stack");
I agree that dying is OK, but as far as I can tell, this is not a
BUG (there is no error a programmer can correct by a follow-up
patch); please do not mark it as such (it is likely that we'll later
do a tree-wide s/die("BUG:/BUG("/ and this will interfere).
> + pcre_assign_jit_stack(p->pcre1_extra_info, NULL, p->pcre1_jit_stack);
> + p->pcre1_jit_on = 1;
Contrary to what I wondered about "canjit" above, I think it makes
tons of sense to contain the "is JIT in use?" information in "struct
grep_pat" and not rely on any global state. Not that we are likely
to want to be able to JIT some patterns while not doing others. So
I agree with the design choice of adding pcre1_jit_on field to the
structure.
But then, wouldn't it make more sense to do all of the above without
the canjit variable at all? i.e. something like...
#ifdef PCRE_CONFIG_JIT
pcre_config(PCRE_CONFIG_JIT, &p->pcre1_jit_on);
if (p->pcre1_jit_on)
... stack thing ...
#else
p->pcre1_jit_on = 0;
#endif
> +#ifdef PCRE_CONFIG_JIT
> + if (p->pcre1_jit_on) {
> + pcre_free_study(p->pcre1_extra_info);
> + pcre_jit_stack_free(p->pcre1_jit_stack);
> + } else
> +#endif
> + /* PCRE_CONFIG_JIT !p->pcre1_jit_on else branch */
> pcre_free(p->pcre1_extra_info);
> +
> pcre_free((void *)p->pcre1_tables);
It is very thoughtful to add a blank line here (and you did the same
in another similar hunk), but I have a feeling that it is still a
bit too subtle a hint to signal to the readers that these two
pcre_free()s fire differently, i.e. the former does not fire if jit
is on but the latter always fires.
Would this be a bit safer while being not too ugly to live, I wonder?
#ifdef PCRE_CONFIG_JIT
if (p->pcre1_jit_on) {
pcre_free_study(p->pcre1_extra_info);
pcre_jit_stack_free(p->pcre1_jit_stack);
} else
#endif
{
/* PCRE_CONFIG_JIT !p->pcre1_jit_on else branch */
pcre_free(p->pcre1_extra_info);
}
pcre_free((void *)p->pcre1_tables);
Thanks.