Better panic diagnostics in Perl_sv_del_backref()

If panicing with a croak(), include in the panic message the values which
caused the croak. This reveals something about the cause of the panic, and
more subtly, which of the two possible panic locations this is.

1 files changed, 3 insertions, 2 deletions

diff --git a/sv.c b/sv.c
index 471caba014..7a11a79145 100644
--- a/sv.c
+++ b/sv.c
@@ -5565,7 +5565,8 @@ Perl_sv_del_backref(pTHX_ SV *const tsv, SV *const sv)
     }
 
     if (!svp || !*svp)
-	Perl_croak(aTHX_ "panic: del_backref");
+	Perl_croak(aTHX_ "panic: del_backref, svp=%p, *svp=%p",
+		   svp, svp ? *svp : NULL);
 
     if (SvTYPE(*svp) == SVt_PVAV) {
 #ifdef DEBUGGING
@@ -5620,7 +5621,7 @@ Perl_sv_del_backref(pTHX_ SV *const tsv, SV *const sv)
     else {
 	/* optimisation: only a single backref, stored directly */
 	if (*svp != sv)
-	    Perl_croak(aTHX_ "panic: del_backref");
+	    Perl_croak(aTHX_ "panic: del_backref, *svp=%p, sv=%p", *svp, sv);
 	*svp = NULL;
     }