Can't use char * for quoted literals. I knew that.

src/google/protobuf/stubs/strutil.cc

@@ -136,7 +136,7 @@ void StripWhitespace(std::string *str) {
                      uintptr_t((dest).size()))
 
 void StringReplace(StringPiece s, StringPiece oldsub, StringPiece newsub,
-                   bool replace_all, std::string *res, char *filename, int linenum) {
+                   bool replace_all, std::string *res, const char *filename, int linenum) {
   if (oldsub.empty()) {
     DONOTCHECKIN_GOOGLE_DCHECK_NO_OVERLAP(*res, s);
     StrAppend(res, s);  // if empty, append the given string.
@@ -171,7 +171,7 @@ void StringReplace(StringPiece s, StringPiece oldsub, StringPiece newsub,
 // ----------------------------------------------------------------------
 
 std::string StringReplaceImpl(StringPiece s, StringPiece oldsub, StringPiece newsub,
-                          bool replace_all, char *filename, int linenum) {
+                          bool replace_all, const char *filename, int linenum) {
   std::string ret;
   StringReplace(s, oldsub, newsub, replace_all, &ret, filename, linenum);
   return ret;

src/google/protobuf/stubs/strutil.h

@@ -205,7 +205,7 @@ inline std::string ToUpper(StringPiece s) {
 // ----------------------------------------------------------------------
 
 PROTOBUF_EXPORT std::string StringReplaceImpl(StringPiece s, StringPiece oldsub,
-                                          StringPiece newsub, bool replace_all, char *filename = nullptr, int linenum = 0);
+                                          StringPiece newsub, bool replace_all, const char *filename = nullptr, int linenum = 0);
 #define StringReplace(s,o,n,all) StringReplaceImpl(s,o,n,all,__FILE__, __LINE__);
 
 // ----------------------------------------------------------------------