first step cleaning up regexp recursion "return" logic

When we do a GOSUB/GOSTART we need to know where the recursion
"returns" to the previous position in the pattern. Currently
this is done by comparing cur_eval->u.eval.close_paren to the
the argument of CLOSE parens, and within END blocks (for GOSTART).

However, there is a problem. The state machinery for GOSUB/GOSTART
is shared with EVAL ( implementing /(??{ ... })/ ), which also sets
cur_eval->u.eval.close_paren to 0. This for instance breaks /(?(R)YES|NO)/
by making it return true within a /(??{ ... })/ when arguably it
shouldn't. It also is confusing.

So we change the meaning of close_paren so that 0 means "from EVAL",
and that otherwise the value is "+1", so 1 means GOSTART (trigger for
END), and 2 means "CLOSE1", etc. In order to make this transparent
this patch adds the EVAL_CLOSE_PAREN_IS( cur_eval, EXPR ) macro which
does the right thing:

    ( cur_eval && cur_eval->u.eval.close_paren &&
      ( ( cur_eval->u.eval.close_paren - 1 ) == EXPR ) )

1 files changed, 8 insertions, 1 deletions

diff --git a/regexp.h b/regexp.h
index 5dbab2e4ed..ff44df27e7 100644
--- a/regexp.h
+++ b/regexp.h
@@ -747,7 +747,7 @@ typedef struct regmatch_state {
 	    REGEXP	*prev_rex;
 	    CHECKPOINT	cp;	/* remember current savestack indexes */
 	    CHECKPOINT	lastcp;
-	    U32        close_paren; /* which close bracket is our end */
+            U32         close_paren; /* which close bracket is our end (+1) */
 	    regnode	*B;	/* the node following us  */
 	} eval;
 
@@ -833,6 +833,13 @@ typedef struct regmatch_state {
     } u;
 } regmatch_state;
 
+#define EVAL_CLOSE_PAREN_IS(cur_eval,expr) \
+(\
+    ( ( cur_eval )                                         ) && \
+    ( ( cur_eval )->u.eval.close_paren                     ) && \
+    ( ( ( cur_eval )->u.eval.close_paren - 1 ) == ( expr ) ) \
+)
+
 /* how many regmatch_state structs to allocate as a single slab.
  * We do it in 4K blocks for efficiency. The "3" is 2 for the next/prev
  * pointers, plus 1 for any mythical malloc overhead. */