Fix silent truncations when extracting values from CheckedNumeric

base/strings/string_number_conversions.cc

 // Copyright (c) 2012 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 "base/strings/string_number_conversions.h"
 
 #include <ctype.h>
 #include <errno.h>
 #include <stdlib.h>
 #include <wctype.h>
@@ skipping 17 matching lines @@
     const size_t kOutputBufSize =
         3 * sizeof(INT) + std::numeric_limits<INT>::is_signed;
 
     // Create the string in a temporary buffer, write it back to front, and
     // then return the substr of what we ended up using.
     using CHR = typename STR::value_type;
     CHR outbuf[kOutputBufSize];
 
     // The ValueOrDie call below can never fail, because UnsignedAbs is valid
     // for all valid inputs.
-    auto res = CheckedNumeric<INT>(value).UnsignedAbs().ValueOrDie();
+    typename decltype(CheckedNumeric<INT>(value).UnsignedAbs())::type res =
+        CheckedNumeric<INT>(value).UnsignedAbs().ValueOrDie();
 
     CHR* end = outbuf + kOutputBufSize;
     CHR* i = end;
     do {
       --i;
       DCHECK(i != outbuf);
       *i = static_cast<CHR>((res % 10) + '0');
       res /= 10;
     } while (res != 0);
     if (IsValueNegative(value)) {
@@ skipping 426 matching lines @@
 bool HexStringToUInt64(const StringPiece& input, uint64_t* output) {
   return IteratorRangeToNumber<HexIteratorRangeToUInt64Traits>::Invoke(
       input.begin(), input.end(), output);
 }
 
 bool HexStringToBytes(const std::string& input, std::vector<uint8_t>* output) {
   return HexStringToBytesT(input, output);
 }
 
 }  // namespace base