Partial fix of bug [perl #17589] : prevent the parser to

segfault when encountering the erroneous construct "sub;".

p4raw-id: //depot/perl@18072

3 files changed, 36 insertions, 1 deletions

diff --git a/pod/perldiag.pod b/pod/perldiag.pod
index 1504fc976f..e1c9a069ab 100644
--- a/pod/perldiag.pod
+++ b/pod/perldiag.pod
@@ -1714,6 +1714,11 @@ to your Perl administrator.
 (W syntax) An illegal character was found in a prototype declaration.  Legal
 characters in prototypes are $, @, %, *, ;, [, ], &, and \.
 
+=item Illegal declaration of anonymous subroutine
+
+(F) When using the C<sub> keyword to construct an anonymous subroutine,
+you must always specify a block of code. See L<perlsub>.
+
 =item Illegal division by zero
 
 (F) You tried to divide a number by 0.  Either something was wrong in
diff --git a/t/op/anonsub.t b/t/op/anonsub.t
index 893a72671c..ddfcd4795d 100755
--- a/t/op/anonsub.t
+++ b/t/op/anonsub.t
@@ -1,5 +1,9 @@
 #!./perl
 
+# Note : we're not using t/test.pl here, because we would need
+# fresh_perl_is, and fresh_perl_is uses a closure -- a special
+# case of what this program tests for.
+
 chdir 't' if -d 't';
 @INC = '../lib';
 $Is_VMS = $^O eq 'VMS';
@@ -12,7 +16,7 @@ $|=1;
 
 undef $/;
 @prgs = split "\n########\n", <DATA>;
-print "1..", scalar @prgs, "\n";
+print "1..", 6 + scalar @prgs, "\n";
 
 $tmpfile = "asubtmp000";
 1 while -f ++$tmpfile;
@@ -51,6 +55,30 @@ for (@prgs){
     print "ok ", ++$i, "\n";
 }
 
+sub test_invalid_decl {
+    my ($code,$todo) = @_;
+    $todo //= '';
+    eval $code;
+    if ($@ =~ /^Illegal declaration of anonymous subroutine at/) {
+	print "ok ", ++$i, " - '$code' is illegal$todo\n";
+    } else {
+	print "not ok ", ++$i, " - '$code' is illegal$todo\n# GOT: $@";
+    }
+}
+
+test_invalid_decl('sub;');
+test_invalid_decl('sub ($) ;');
+test_invalid_decl('{ $x = sub }');
+test_invalid_decl('sub ($) && 1');
+test_invalid_decl('sub ($) : lvalue;',' # TODO');
+
+eval "sub #foo\n{print 1}";
+if ($@ eq '') {
+    print "ok ", ++$i, "\n";
+} else {
+    print "not ok ", ++$i, "\n# GOT: $@";
+}
+
 __END__
 sub X {
     my $n = "ok 1\n";
diff --git a/toke.c b/toke.c
index d95b0a72bb..aff4549138 100644
--- a/toke.c
+++ b/toke.c
@@ -5057,6 +5057,8 @@ Perl_yylex(pTHX)
 
 		if (*s == ':' && s[1] != ':')
 		    PL_expect = attrful;
+		else if (!have_name && *s != '{' && key == KEY_sub)
+		    Perl_croak(aTHX_ "Illegal declaration of anonymous subroutine");
 
 		if (have_proto) {
 		    PL_nextval[PL_nexttoke].opval =