bad things happened with for $x (...) { *x = *y }

fix for [perl #21469]:
since the GP may be pulled from under us and freed, coredumps and strange
things can happen.

Fix this by storing a pointer to the GV in the loop block, rather than a
pointer to the GvSV slot. The ITHREADS variant already stores GV rather
than than &GvSV; extend this to non-threaded builds too.

Also, for both threaded and non-threaded, it used to push &GvSV on the
save stack. Fix this by introducing a new save type, SAVEt_GVSV.
This behaves similarly to SAVEt_SV, but without magic get/set.

This means that

    for $package_var (...)

is now close in behaviour to

    local $package_var = ...

(except for the magic bit).

1 files changed, 2 insertions, 5 deletions

diff --git a/pp_ctl.c b/pp_ctl.c
index b2c68d360a..155313e295 100644
--- a/pp_ctl.c
+++ b/pp_ctl.c
@@ -1967,13 +1967,10 @@ PP(pp_enteriter)
     }
     else {					/* symbol table variable */
 	GV * const gv = MUTABLE_GV(POPs);
-	SV** svp = &GvSV(gv);	SAVEGENERICSV(*svp);
+	SV** svp = &GvSV(gv);
+	save_pushptrptr(gv, SvREFCNT_inc(*svp), SAVEt_GVSV);
 	*svp = newSV(0);
-#ifdef USE_ITHREADS
 	itervar = (void *)gv;
-#else
-	itervar = (void *)svp;
-#endif
     }
 
     if (PL_op->op_private & OPpITER_DEF)