[perl #123852] avoid capture side-effects under noncapture flag

//n was implemented by avoiding the primary side-effects of compiling
a capture when the flag was turned on; however some secondary effects
still occurred later in the same function, by using the value of the
'paren' variable - even as far as causing coredumps.

Setting paren to ':' when NOCAPTURE is enabled makes the rest of the
function act just as if it had parsed (?:...) instead of (...).

1 files changed, 2 insertions, 0 deletions

diff --git a/regcomp.c b/regcomp.c
index 51c778d044..68f6bfdc43 100644
--- a/regcomp.c
+++ b/regcomp.c
@@ -10450,6 +10450,8 @@ S_reg(pTHX_ RExC_state_t *pRExC_state, I32 paren, I32 *flagp,U32 depth)
             Set_Node_Offset(ret, RExC_parse); /* MJD */
 	    is_open = 1;
 	} else {
+            /* with RXf_PMf_NOCAPTURE treat (...) as (?:...) */
+            paren = ':';
 	    ret = NULL;
 	}
     }