regcomp.c: Make SSC node clone safe

This just sets the ptr field in the Synthetic Start Class that will be
passed to regexec.c NULL, and clarifies the comments in regcomp.h.  See
the thread starting at http://markmail.org/message/2txwaqnjco6zodeo

1 files changed, 13 insertions, 9 deletions

diff --git a/regcomp.h b/regcomp.h
index 700d6c197d..3bb1a533f6 100644
--- a/regcomp.h
+++ b/regcomp.h
@@ -217,14 +217,15 @@ struct regnode_charclass_class {
     U32 classflags;	                        /* and run-time */
 };
 
-/* A synthetic start class; is a regnode_charclass_posixl_fold, plus an extra
- * SV*, used only during its construction and which is not used by regexec.c.
- * Note that the 'next_off' field is unused, as the SSC stands alone, so there
- * is never a next node.  Also, there is no alignment issue, becase these are
- * declared or allocated as a complete unit so the compiler takes care of
- * alignment.  This is unlike ithe other regnodes which are allocated in terms
- * of multiples of a single-argument regnode.  Because there is no alignment
- * issue, these can have a pointer field */
+/* A synthetic start class (SSC); is a regnode_charclass_posixl_fold, plus an
+ * extra SV*, used only during its construction and which is not used by
+ * regexec.c.  Note that the 'next_off' field is unused, as the SSC stands
+ * alone, so there is never a next node.  Also, there is no alignment issue,
+ * becase these are declared or allocated as a complete unit so the compiler
+ * takes care of alignment.  This is unlike the other regnodes which are
+ * allocated in terms of multiples of a single-argument regnode.  SSC nodes can
+ * have a pointer field because there is no alignment issue, and because it is
+ * set to NULL after construction, before any cloning of the pattern */
 struct regnode_ssc {
     U8	flags;				/* ANYOF_POSIXL bit must go here */
     U8  type;
@@ -232,7 +233,10 @@ struct regnode_ssc {
     U32 arg1;
     char bitmap[ANYOF_BITMAP_SIZE];	/* both compile-time */
     U32 classflags;	                /* and run-time */
-    SV* invlist;                        /* list of code points matched */
+
+    /* Auxiliary, only used during construction; NULL afterwards: list of code
+     * points matched */
+    SV* invlist;
 };
 
 /*  We take advantage of 'next_off' not otherwise being used in the SSC by