assert that the RExC_recurse data structure points at a valid GOSUB

This assert will fail if someone adds code that optimises away a GOSUB
call. At which point they will see the comment and know what to do.

1 files changed, 12 insertions, 0 deletions

diff --git a/regcomp.c b/regcomp.c
index d5ce63fe27..19ed866f84 100644
--- a/regcomp.c
+++ b/regcomp.c
@@ -7789,6 +7789,18 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
 
     while ( RExC_recurse_count > 0 ) {
         const regnode *scan = RExC_recurse[ --RExC_recurse_count ];
+        /*
+         * This data structure is set up in study_chunk() and is used
+         * to calculate the distance between a GOSUB regopcode and
+         * the OPEN/CURLYM (CURLYM's are special and can act like OPEN's)
+         * it refers to.
+         *
+         * If for some reason someone writes code that optimises
+         * away a GOSUB opcode then the assert should be changed to
+         * an if(scan) to guard the ARG2L_SET() - Yves
+         *
+         */
+        assert(scan && OP(scan) == GOSUB);
         ARG2L_SET( scan, RExC_open_parens[ARG(scan)] - scan );
     }