Go patch committed: check for invalid UTF-8 in line comments

[Ian Lance Taylor]

This patch by Chris Manghane fixes the Go compiler to check for
invalid UTF-8 in line comments.  Otherwise the compiler might pass a
file that it shouldn't.  This fixes https://golang.org/issue/11527 .
Bootstrapped and ran Go testsuite on x86_64-unknown-linux-gnu.
Committed to mainline.

Ian

Index: gcc/go/gofrontend/MERGE
===================================================================
--- gcc/go/gofrontend/MERGE     (revision 227299)
+++ gcc/go/gofrontend/MERGE     (working copy)
@@ -1,4 +1,4 @@
-3aa2ea272e475010da8b480fc3095d0cd7254d12
+65672c16004c6d6d0247b6691881d282ffca89e3
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.
Index: gcc/go/gofrontend/lex.cc
===================================================================
--- gcc/go/gofrontend/lex.cc    (revision 227299)
+++ gcc/go/gofrontend/lex.cc    (working copy)
@@ -1689,6 +1689,16 @@ Lex::skip_cpp_comment()
       && memcmp(p, "line ", 5) == 0)
     {
       p += 5;
+
+      // Before finding FILE:LINENO, make sure line has valid characters.
+      const char* pcheck = p;
+      while (pcheck < pend)
+        {
+          unsigned int c;
+          bool issued_error;
+          pcheck = this->advance_one_utf8_char(pcheck, &c, &issued_error);
+        }
+
       while (p < pend && *p == ' ')
        ++p;
       const char* pcolon = static_cast<const char*>(memchr(p, ':', pend - p));