Stop uninit sort warnings from crashing

Commit d4c6760a made the warning in cases like this mention the
sort operator:

$ ./miniperl -we '()=sort { undef } 1,2'
Use of uninitialized value [in sort] at -e line 1.

It did so by setting PL_op during the SvIV(retval of sort block).  But
sv.c:S_find_uninit_var, called by report_uninit, tries to access the
targets of some ops, which are in PL_curpad on threaded builds.  In
the case of a sort sub (rather than an inlined block), PL_curpad con-
tained whatever was left over from the sort block (I presume, but
have not confirmed; in any case what is in PL_curpad is bad), causing
find_uninit_var to crash.

This commit sets PL_curpad to null and puts a check for it in
report_uninit.

It did not crash in debugging threaded builds, but that was probably
luck (even though I don’t believe in it).

1 files changed, 1 insertions, 1 deletions

diff --git a/sv.c b/sv.c
index e0bcfdfb18..5ee48175b2 100644
--- a/sv.c
+++ b/sv.c
@@ -14314,7 +14314,7 @@ Perl_report_uninit(pTHX_ const SV *uninit_sv)
     dVAR;
     if (PL_op) {
 	SV* varname = NULL;
-	if (uninit_sv) {
+	if (uninit_sv && PL_curpad) {
 	    varname = find_uninit_var(PL_op, uninit_sv,0);
 	    if (varname)
 		sv_insert(varname, 0, 0, " ", 1);