make PL_reg_curpm global

Currently PL_reg_curpm is actually #deffed to a field within PL_reg_state;
promote it into a fully autonomous perl-interpreter variable.

PL_reg_curpm points to a fake PMOP that's used to temporarily point
PL_curpm to, that we can hang the current regex off, so that this works:

    "a" =~ /^(.)(?{ print $1 })/ # prints 'a'

It turns out that it doesn't need to be saved and restored when we
recursively enter the regex engine; that is already handled by saving and
restoring which regex is currently attached to PL_reg_curpm.
So we just need a single global (per interpreter) placeholder.

Since we're shortly going to get rid of PL_reg_state, we need to move it
out of that struct.

1 files changed, 3 insertions, 0 deletions

diff --git a/intrpvar.h b/intrpvar.h
index a148a3c412..32a9983e41 100644
--- a/intrpvar.h
+++ b/intrpvar.h
@@ -121,6 +121,9 @@ PERLVAR(I, sv_arenaroot, SV *)		/* list of areas for garbage collection */
 
 PERLVAR(I, reg_state,	struct re_save_state)
 
+/* fake PMOP that PL_curpm points to while in (?{}) so $1 et al are visible */
+PERLVARI(I, reg_curpm, PMOP*, NULL)
+
 /* the currently active slab in a chain of slabs of regmatch states,
  * and the currently active state within that slab */