add strbeg argument to Perl_re_intuit_start()

(note that this is a change both to the perl API and the regex engine
plugin API).

Currently, Perl_re_intuit_start() is passed an SV, plus pointers to:
where in the string to start matching (strpos); and to the end of the
string (strend).

Unlike Perl_regexec_flags(), it doesn't also have a strbeg arg.
Because of this this, it guesses strbeg: based on the passed SV (if its
svPOK()); or just set to strpos otherwise. This latter can happen if for
example the SV is overloaded. Note also that this latter guess is wrong,
and could in theory make /\b.../ fail.

But just to confuse matters, although Perl_re_intuit_start() itself uses
its guesstimate strbeg var, some of the functions it calls use the global
value of PL_bostr instead. To make this work, the *callers* of
Perl_re_intuit_start() currently set PL_bostr first. This is why \b
doesn't actually break.

The fix to this unholy mess is to simply add a strbeg arg to
Perl_re_intuit_start(). It's also the first step to eliminating PL_bostr
altogether.

1 files changed, 7 insertions, 2 deletions

diff --git a/regexp.h b/regexp.h
index 3479f260cf..72d233999d 100644
--- a/regexp.h
+++ b/regexp.h
@@ -157,8 +157,13 @@ typedef struct regexp_engine {
     I32     (*exec) (pTHX_ REGEXP * const rx, char* stringarg, char* strend,
                      char* strbeg, I32 minend, SV* screamer,
                      void* data, U32 flags);
-    char*   (*intuit) (pTHX_ REGEXP * const rx, SV *sv, char *strpos,
-                       char *strend, const U32 flags,
+    char*   (*intuit) (pTHX_
+                        REGEXP * const rx,
+                        SV *sv,
+                        const char * const strbeg,
+                        char *strpos,
+                        char *strend,
+                        const U32 flags,
                        re_scream_pos_data *data);
     SV*     (*checkstr) (pTHX_ REGEXP * const rx);
     void    (*free) (pTHX_ REGEXP * const rx);