[RFC PATCH v3] grep: treat PCRE2 jit compilation memory error as non fatal

["Carlo Marcelo Arenas Belón" <carenas@gmail.com>]

94da9193a6 (grep: add support for PCRE v2, 2017-06-01) uses the
JIT fast path unless JIT support has not been compiled in the
linked library.

Starting from 10.23 of PCRE2, pcre2grep ignores any errors from
pcre2_jit_cpmpile as a workaround for their bug1749[1] and we
should do too, so that the interpreter could be used as a fallback
in cases where JIT was not available because of a security policy.

To be conservative, we are restricting initially the error to the
known error that would be returned in that case (and to be documented
as such in a future release of PCRE) and printing a warning so that
corrective action could be taken.

[1] https://bugs.exim.org/show_bug.cgi?id=1749

Signed-off-by: Carlo Marcelo Arenas Belón <carenas@gmail.com>
---
 grep.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/grep.c b/grep.c
index f7c3a5803e..593a1cb7a0 100644
--- a/grep.c
+++ b/grep.c
@@ -525,7 +525,13 @@ static void compile_pcre2_pattern(struct grep_pat *p, const struct grep_opt *opt
 	if (p->pcre2_jit_on == 1) {
 		jitret = pcre2_jit_compile(p->pcre2_pattern, PCRE2_JIT_COMPLETE);
 		if (jitret)
-			die("Couldn't JIT the PCRE2 pattern '%s', got '%d'\n", p->pattern, jitret);
+			if (jitret == PCRE2_ERROR_NOMEMORY) {
+				warning("JIT couldn't be used in PCRE2");
+				p->pcre2_jit_on = 0;
+				return;
+			}
+			else
+				die("Couldn't JIT the PCRE2 pattern '%s', got '%d'\n", p->pattern, jitret);
 
 		/*
 		 * The pcre2_config(PCRE2_CONFIG_JIT, ...) call just
-- 
2.23.0.rc1