compiler, runtime: Reject surrogate pair converting int to string.

From-SVN: r191636

gcc/go/gofrontend/lex.cc

@@ -1312,6 +1312,12 @@ Lex::append_char(unsigned int v, bool is_character, std::string* str,
 	  // Turn it into the "replacement character".
 	  v = 0xfffd;
 	}
+      if (v >= 0xd800 && v < 0xe000)
+	{
+	  warning_at(location, 0,
+		     "unicode code point 0x%x is invalid surrogate pair", v);
+	  v = 0xfffd;
+	}
       if (v <= 0xffff)
 	{
 	  buf[0] = 0xe0 + (v >> 12);

libgo/runtime/go-int-to-string.c

@@ -17,6 +17,11 @@ __go_int_to_string (int v)
   unsigned char *retdata;
   struct __go_string ret;
 
+  /* A negative value is not valid UTF-8; turn it into the replacement
+     character.  */
+  if (v < 0)
+    v = 0xfffd;
+
   if (v <= 0x7f)
     {
       buf[0] = v;
@@ -34,6 +39,10 @@ __go_int_to_string (int v)
 	 "replacement character".  */
       if (v > 0x10ffff)
 	v = 0xfffd;
+      /* If the value is a surrogate pair, which is invalid in UTF-8,
+	 turn it into the replacement character.  */
+      if (v >= 0xd800 && v < 0xe000)
+	v = 0xfffd;
 
       if (v <= 0xffff)
 	{