Make open(... "<&", $fileno) respect magic

A magical variable is never SvPOK, but only SvPOKp.  The code for
checking whether a duplicatee is a numeric file descriptor was only
checking SvPOK.  So a regular variable containing a fileno-as-a-string
would work, such as the $a below, as would a stringified magical vari-
able ("$1"), but not $1 itself.

$ echo foo | perl -le '$a = "0"; open a, "<&", $a; warn <a>'
foo
$ echo foo | perl -le '"0" =~ /(.)/; open a, "<&", $1; warn <a>'
Can't use an undefined value as filehandle reference at -e line 1.
$ echo foo | perl -le '"0" =~ /(.)/; open a, "<&", "$1"; warn <a>'
foo

SvPOK variables are also SvPOKp, so checking only the latter suffices.

1 files changed, 4 insertions, 1 deletions

diff --git a/doio.c b/doio.c
index 69d091c219..fed1a49455 100644
--- a/doio.c
+++ b/doio.c
@@ -320,7 +320,10 @@ Perl_do_openn(pTHX_ GV *gv, register const char *oname, I32 len, int as_raw,
 		    }
 		    while (isSPACE(*type))
 			type++;
-		    if (num_svs && (SvIOK(*svp) || (SvPOK(*svp) && looks_like_number(*svp)))) {
+		    if (num_svs && (
+			     SvIOK(*svp)
+			  || (SvPOKp(*svp) && looks_like_number(*svp))
+		       )) {
 			fd = SvUV(*svp);
 			num_svs = 0;
 		    }