X-Git-Url: https://perl5.git.perl.org/perl5.git/blobdiff_plain/d20626d86bf3d55ba658adbc2678de4c519cbc6c..237671e544fe54ad7ff79d35f6685fe38cccc4d0:/universal.c?ds=sidebyside

diff --git a/universal.c b/universal.c
index aa5487f..6ccff2f 100644
--- a/universal.c
+++ b/universal.c
@@ -73,6 +73,16 @@ S_isa_lookup(pTHX_ HV *stash, const char *name, int len, int level)
     return boolSV(strEQ(name, "UNIVERSAL"));
 }
 
+/*
+=for apidoc sv_derived_from
+
+Returns a boolean indicating whether the SV is derived from the specified
+class.  This is the function that implements C<UNIVERSAL::isa>.  It works
+for class names as well as for objects.
+
+=cut
+*/
+
 bool
 Perl_sv_derived_from(pTHX_ SV *sv, const char *name)
 {
@@ -130,6 +140,10 @@ XS(XS_UNIVERSAL_isa)
 	Perl_croak(aTHX_ "Usage: UNIVERSAL::isa(reference, kind)");
 
     sv = ST(0);
+
+    if (!SvOK(sv) || !(SvROK(sv) || SvCUR(sv)))
+	XSRETURN_UNDEF;
+
     name = (char *)SvPV(ST(1),n_a);
 
     ST(0) = boolSV(sv_derived_from(sv, name));
@@ -149,6 +163,10 @@ XS(XS_UNIVERSAL_can)
 	Perl_croak(aTHX_ "Usage: UNIVERSAL::can(object-ref, method)");
 
     sv = ST(0);
+
+    if (!SvOK(sv) || !(SvROK(sv) || SvCUR(sv)))
+	XSRETURN_UNDEF;
+
     name = (char *)SvPV(ST(1),n_a);
     rv = &PL_sv_undef;