add PL_curstackinfo->si_cxsubix field

This tracks the most recent sub/eval/format context pushed onto the
context stack. Then make dopopto_cursub use it.

The previous value is saved in the cxt struct, and is restored whenever
the context is popped.

This adds a tiny overhead for every sub call, but speeds up other
operations, such as determining the caller context when returning a
value from a sub - this has to be dpne for every sub call where the last
expression is context sensitive, so its often a win.

1 files changed, 1 insertions, 0 deletions

diff --git a/scope.c b/scope.c
index 9b1393c69d..c6616440f6 100644
--- a/scope.c
+++ b/scope.c
@@ -82,6 +82,7 @@ Perl_new_stackinfo(pTHX_ I32 stitems, I32 cxitems)
     si->si_next = 0;
     si->si_cxmax = cxitems - 1;
     si->si_cxix = -1;
+    si->si_cxsubix = -1;
     si->si_type = PERLSI_UNDEF;
     Newx(si->si_cxstack, cxitems, PERL_CONTEXT);
     /* Without any kind of initialising CX_PUSHSUBST()