Eliminate PL_reg_state.re_reparsing, part 1

PL_reg_state.re_reparsing is a hacky flag used to allow runtime
code blocks to be included in patterns. Basically, since code blocks
are now handled by the perl parser within literal patterns, runtime
patterns are handled by taking the (assembled at runtime) pattern,
and feeding it back through the parser via the equivalent of
    eval q{qr'the_pattern'},
so that run-time (?{..})'s appear to be literal code blocks.
When this happens, the global flag PL_reg_state.re_reparsing is set,
which modifies lexing and parsing in minor ways (such as whether \\ is
stripped).

Now, I'm in the slow process of trying to eliminate global regex state
(i.e. gradually removing the fields of PL_reg_state), and also a change
which will be coming a few commits ahead requires the info which this flag
indicates to linger for longer (currently it is cleared immediately after
the call to scan_str().

For those two reasons, this commit adds a new mechanism to indicate this:
a new flag to eval_sv(), G_RE_REPARSING (which sets OPpEVAL_RE_REPARSING
in the entereval op), which sets the EVAL_RE_REPARSING bit in PL_in_eval.

Its still a yukky global flag hack, but its a *different* global flag hack
now.

For this commit, we add the new flag(s) but keep the old
PL_reg_state.re_reparsing flag and assert that the two mechanisms always
match. The next commit will remove re_reparsing.

1 files changed, 2 insertions, 0 deletions

diff --git a/cop.h b/cop.h
index 086cd22dd0..b20eddbde0 100644
--- a/cop.h
+++ b/cop.h
@@ -1048,6 +1048,7 @@ L<perlcall>.
 				   Perl_magic_methcall().  */
 #define G_WRITING_TO_STDERR 1024 /* Perl_write_to_stderr() is calling
 				    Perl_magic_methcall().  */
+#define G_RE_REPARSING 0x800     /* compiling a run-time /(?{..})/ */
 
 /* flag bits for PL_in_eval */
 #define EVAL_NULL	0	/* not in an eval */
@@ -1055,6 +1056,7 @@ L<perlcall>.
 #define EVAL_WARNONLY	2	/* used by yywarn() when calling yyerror() */
 #define EVAL_KEEPERR	4	/* set by Perl_call_sv if G_KEEPERR */
 #define EVAL_INREQUIRE	8	/* The code is being required. */
+#define EVAL_RE_REPARSING 0x10	/* eval_sv() called with G_RE_REPARSING */
 
 /* Support for switching (stack and block) contexts.
  * This ensures magic doesn't invalidate local stack and cx pointers.