[perl #94390] Optimised numeric sort should warn for nan

In this case:

    sort { $a <=> $b } ...

the sort block is optimised away and implemented in C.

That C implementation did not take into account that $a or $b might be
nan, and therefore, without optimisation, would return undef, result-
ing in a warning.

The optimisation is supposed to be just that, and not change
behaviour.

1 files changed, 8 insertions, 0 deletions

diff --git a/pp_sort.c b/pp_sort.c
index fafa00acf2..0ee42dcf38 100644
--- a/pp_sort.c
+++ b/pp_sort.c
@@ -1874,6 +1874,14 @@ S_sv_ncmp(pTHX_ SV *const a, SV *const b)
 
     PERL_ARGS_ASSERT_SV_NCMP;
 
+#if defined(NAN_COMPARE_BROKEN) && defined(Perl_isnan)
+    if (Perl_isnan(right) || Perl_isnan(left)) {
+#else
+    if (nv1 != nv1 || nv2 != nv2) {
+#endif
+	if (ckWARN(WARN_UNINITIALIZED)) report_uninit(NULL);
+	return 0;
+    }
     return nv1 < nv2 ? -1 : nv1 > nv2 ? 1 : 0;
 }