Fix for

Subject: [ID 20001004.006] undef is never tainted
Message-Id: <m13h0I3-000SEmC@nolfolan.idiomtech.com>

An undef read from a slurped file was not tainted.

p4raw-id: //depot/perl@7549

2 files changed, 20 insertions, 6 deletions

diff --git a/pp_hot.c b/pp_hot.c
index 3f85116a31..b0d53bcc20 100644
--- a/pp_hot.c
+++ b/pp_hot.c
@@ -1450,6 +1450,13 @@ Perl_do_readline(pTHX)
 	offset = 0;
     }
 
+    /* This should not be marked tainted if the fp is marked clean */
+#define MAYBE_TAINT_LINE(io, sv) \
+    if (!(IoFLAGS(io) & IOf_UNTAINT)) { \
+	TAINT;				\
+	SvTAINTED_on(sv);		\
+    }
+
 /* delay EOF state for a snarfed empty file */
 #define SNARF_EOF(gimme,rs,io,sv) \
     (gimme != G_SCALAR || SvCUR(sv)					\
@@ -1478,13 +1485,10 @@ Perl_do_readline(pTHX)
 		(void)SvOK_off(TARG);
 		PUSHTARG;
 	    }
+	    MAYBE_TAINT_LINE(io, sv);
 	    RETURN;
 	}
-	/* This should not be marked tainted if the fp is marked clean */
-	if (!(IoFLAGS(io) & IOf_UNTAINT)) {
-	    TAINT;
-	    SvTAINTED_on(sv);
-	}
+	MAYBE_TAINT_LINE(io, sv);
 	IoLINES(io)++;
 	IoFLAGS(io) |= IOf_NOLINE;
 	SvSETMAGIC(sv);
diff --git a/t/op/taint.t b/t/op/taint.t
index 7cc4447a0b..fc3a595c4e 100755
--- a/t/op/taint.t
+++ b/t/op/taint.t
@@ -99,7 +99,7 @@ print PROG 'print "@ARGV\n"', "\n";
 close PROG;
 my $echo = "$Invoke_Perl $ECHO";
 
-print "1..151\n";
+print "1..152\n";
 
 # First, let's make sure that Perl is checking the dangerous
 # environment variables. Maybe they aren't set yet, so we'll
@@ -681,3 +681,13 @@ else {
     }
 }
 
+{
+    # bug id 20001004.006
+
+    open IN, "./TEST" or warn "$0: cannot read ./TEST: $!" ;
+    local $/;
+    my $a = <IN>;
+    my $b = <IN>;
+    print "not " unless tainted($a) && tainted($b) && !defined($b);
+    print "ok 152\n";
+}