encoding.c: handle needmore error from rb_enc_precise_mbclen()

rb_enc_ascget() erroneously reports success even if the given byte
sequence is incomplete, for non-ASCII compatible encoding strings.

rb_enc_precise_mbclen() may return a negative value on error, and thus
rb_enc_ascget() must not store the return value in 'unsigned int';
otherwise the subsequent MBCLEN_CHARFOUND_P() check won't catch the
error.  [ruby-core:78646] [Bug #13034]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57078 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

encoding.c

@@ -1031,7 +1031,8 @@ rb_enc_precise_mbclen(const char *p, const char *e, rb_encoding *enc)
 int
 rb_enc_ascget(const char *p, const char *e, int *len, rb_encoding *enc)
 {
-    unsigned int c, l;
+    unsigned int c;
+    int l;
     if (e <= p)
         return -1;
     if (rb_enc_asciicompat(enc)) {

test/ruby/test_regexp.rb

@@ -567,6 +567,10 @@ def test_quote
     assert_equal("\\v", Regexp.quote("\v"))
     assert_equal("\u3042\\t", Regexp.quote("\u3042\t"))
     assert_equal("\\t\xff", Regexp.quote("\t" + [0xff].pack("C")))
+
+    bug13034 = '[ruby-core:78646] [Bug #13034]'
+    str = "\x00".force_encoding("UTF-16BE")
+    assert_equal(str, Regexp.quote(str), bug13034)
   end
 
   def test_try_convert