Assertion failure with $/=*foo; warn;

$ ./perl -Ilib -e '$/=*foo; <>; warn' <./perl
Assertion failed: (!isGV_with_GP(_svcur)), function Perl_mess_sv, file util.c, line 1467.
Abort trap

The assertion happens when ‘<...> line 42’ is being appended to
the message.

The line of code in question is this:

	    const bool line_mode = (RsSIMPLE(PL_rs) &&
			      SvCUR(PL_rs) == 1 && *SvPVX_const(PL_rs) == '\n');

It uses this macro in perl.h:

#define RsSIMPLE(sv)  (SvOK(sv) && (! SvPOK(sv) || SvCUR(sv)))

which was last modified by commit af7d13df559:

-#define RsSIMPLE(sv)  (SvOK(sv) && SvCUR(sv))
-#define RsPARA(sv)    (SvOK(sv) && ! SvCUR(sv))
+#define RsSIMPLE(sv)  (SvOK(sv) && (! SvPOK(sv) || SvCUR(sv)))
+#define RsPARA(sv)    (SvPOK(sv) && ! SvCUR(sv))

So it looks as though it has always called SvCUR on something that is
not necessarily a PV.  As of commit af7d13df559, it has also called
SvPVX on a potential non-PV.

Fixing this simply involves using SvPV instead of SvPVX.

I don’t know that t/io/open.t is the best place for the test, but all
the other ‘<...> line 42’ tests are there.

1 files changed, 2 insertions, 1 deletions

diff --git a/util.c b/util.c
index d0fea67dd1..9c9c07283e 100644
--- a/util.c
+++ b/util.c
@@ -1306,8 +1306,9 @@ Perl_mess_sv(pTHX_ SV *basemsg, bool consume)
 	if (GvIO(PL_last_in_gv) && (SvTYPE(GvIOp(PL_last_in_gv)) == SVt_PVIO)
 		&& IoLINES(GvIOp(PL_last_in_gv)))
 	{
+	    STRLEN l;
 	    const bool line_mode = (RsSIMPLE(PL_rs) &&
-			      SvCUR(PL_rs) == 1 && *SvPVX_const(PL_rs) == '\n');
+				   *SvPV_const(PL_rs,l) == '\n' && l == 1);
 	    Perl_sv_catpvf(aTHX_ sv, ", <%"SVf"> %s %"IVdf,
 			   SVfARG(PL_last_in_gv == PL_argvgv
                                  ? &PL_sv_no