regcomp.c - add optimistic eval (*{ ... }) and (**{ ... })

This adds (*{ ... }) and (**{ ... }) as equivalents to (?{ ... }) and
(??{ ... }). The only difference being that the star variants are
"optimisitic" and are defined to never disable optimisations. This is
especially relevant now that use of (?{ ... }) prevents important
optimisations anywhere in the pattern, instead of the older and inconsistent
rules where it only affected the parts that contained the EVAL.

It is also very useful for injecting debugging style expressions to the
pattern to understand what the regex engine is actually doing. The older
style (?{ ... }) variants would change the regex engines behavior, meaning
this was not as effective a tool as it could have been.

Similarly it is now possible to test that a given regex optimisation
works correctly using (*{ ... }), which was not possible with (?{ ... }).

1 files changed, 1 insertions, 1 deletions

diff --git a/regexec.c b/regexec.c
index a022098380..8a54cfa44f 100644
--- a/regexec.c
+++ b/regexec.c
@@ -8585,7 +8585,7 @@ S_regmatch(pTHX_ regmatch_info *reginfo, char *startpos, regnode *prog)
             break;
 
         case LOGICAL:  /* modifier for EVAL and IFMATCH */
-            logical = scan->flags;
+            logical = scan->flags & EVAL_FLAGS_MASK; /* reserve a bit for optimistic eval */
             break;
 
 /*******************************************************************