tools/gn: disallow non-canonical integer literals

tools/gn/parse_tree.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "tools/gn/parse_tree.h"
 
 #include <string>
 
 #include "base/stl_util.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 616 matching lines @@
   return this;
 }
 
 Value LiteralNode::Execute(Scope* scope, Err* err) const {
   switch (value_.type()) {
     case Token::TRUE_TOKEN:
       return Value(this, true);
     case Token::FALSE_TOKEN:
       return Value(this, false);
     case Token::INTEGER: {
+      base::StringPiece s = value_.value();
+      if ((s.starts_with("0") && s.size() > 1) || s.starts_with("-0")) {
+        if (s == "-0")
+          *err = MakeErrorDescribing("Negative zero doesn't make sense");
+        else
+          *err = MakeErrorDescribing("Leading zeros not allowed");
+        return Value();
+      }
       int64 result_int;
-      if (!base::StringToInt64(value_.value(), &result_int)) {
+      if (!base::StringToInt64(s, &result_int)) {
         *err = MakeErrorDescribing("This does not look like an integer");
         return Value();
       }
       return Value(this, result_int);
     }
     case Token::STRING: {
       Value v(this, Value::STRING);
       ExpandStringLiteral(scope, value_, &v, err);
       return v;
     }
@@ skipping 109 matching lines @@
 
 Err EndNode::MakeErrorDescribing(const std::string& msg,
                                         const std::string& help) const {
   return Err(value_, msg, help);
 }
 
 void EndNode::Print(std::ostream& out, int indent) const {
   out << IndentFor(indent) << "END(" << value_.value() << ")\n";
   PrintComments(out, indent);
 }