Don’t use strchr when scanning for newline after <<foo

The code that uses this is specifically for parsing <<foo inside a
quote-like operator inside a string eval.

This prints bar:

eval "s//<<foo/e
bar
foo
";
print $_ || $@;

This prints Can't find string terminator blah blah blah:

eval "s//<<foo/e #\0
bar
foo
";
print $_ || $@;

Nulls in comments are allowed elsewhere.  This prints bar:

eval "\$_ = <<foo #\0
bar
foo
";
print $_ || $@;

The problem with strchr is that it is specifically for scanning null-
terminated strings.  If embedded nulls are permitted (and should be in
this case), memchr should be used.

This code was added by 0244c3a403.

2 files changed, 9 insertions, 2 deletions

diff --git a/t/base/lex.t b/t/base/lex.t
index 559cc30021..2baa5dacff 100644
--- a/t/base/lex.t
+++ b/t/base/lex.t
@@ -1,6 +1,6 @@
 #!./perl
 
-print "1..59\n";
+print "1..60\n";
 
 $x = 'x';
 
@@ -288,3 +288,10 @@ END
 |e
 ';
 print $_ || "not ok 59\n";
+
+$_ = "";
+eval "s/(?:)/<<foo/e #\0
+ok 60 - null on same line as heredoc in s/// in eval
+foo
+";
+print $_ || "not ok 60\n";
diff --git a/toke.c b/toke.c
index 6b1a8aecc3..ab7939404f 100644
--- a/toke.c
+++ b/toke.c
@@ -9605,7 +9605,7 @@ S_scan_heredoc(pTHX_ register char *s)
 	char * const bufend = SvEND(PL_sublex_info.super_linestr);
 	char * const olds = s - SvCUR(herewas);
 	term = *PL_tokenbuf;
-	s = strchr(bufptr, '\n');
+	s = (char *)memchr((void *)bufptr, '\n', bufend-bufptr);
 	if (!s)
 	    s = bufend;
 	d = s;