Add note to debugging output if regex already compiled

Prior to this commit, the debugging output says "Compiling REx foo".
But there was no indication that it was skipped due to the pattern
already being compiled; so that was confusing to people, and was a Stack
Overflow question of what is going on.  Now there's an extra message
that the recompilation is skipped.

diff --git a/regcomp.c b/regcomp.c
index b389f9e..c770f9d 100644 (file)
--- a/regcomp.c
+++ b/regcomp.c
@@ -7584,6 +7584,12 @@ Perl_re_op_compile(pTHX_ SV ** const patternp, int pat_count,
         && memEQ(RX_PRECOMP(old_re), exp, plen)
        && !runtime_code /* with runtime code, always recompile */ )
     {
+        DEBUG_COMPILE_r({
+            SV *dsv= sv_newmortal();
+            RE_PV_QUOTED_DECL(s, RExC_utf8, dsv, exp, plen, PL_dump_re_max_len);
+            Perl_re_printf( aTHX_  "%sSkipping recompilation of unchanged REx%s %s\n",
+                          PL_colors[4], PL_colors[5], s);
+        });
         return old_re;
     }