Make UBSan happy.

src/strtod.cc

 // Copyright 2012 the V8 project 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 <stdarg.h>
 #include <cmath>
 
 #include "src/v8.h"
 
 #include "src/bignum.h"
@@ skipping 229 matching lines @@
   ReadDiyFp(buffer, &input, &remaining_decimals);
   // Since we may have dropped some digits the input is not accurate.
   // If remaining_decimals is different than 0 than the error is at most
   // .5 ulp (unit in the last place).
   // We don't want to deal with fractions and therefore keep a common
   // denominator.
   const int kDenominatorLog = 3;
   const int kDenominator = 1 << kDenominatorLog;
   // Move the remaining decimals into the exponent.
   exponent += remaining_decimals;
-  int error = (remaining_decimals == 0 ? 0 : kDenominator / 2);
+  int64_t error = (remaining_decimals == 0 ? 0 : kDenominator / 2);
 
   int old_e = input.e();
   input.Normalize();
   error <<= old_e - input.e();
 
   ASSERT(exponent <= PowersOfTenCache::kMaxDecimalExponent);
   if (exponent < PowersOfTenCache::kMinDecimalExponent) {
     *result = 0.0;
     return true;
   }
@@ skipping 152 matching lines @@
 
   double guess;
   if (DoubleStrtod(trimmed, exponent, &guess) ||
       DiyFpStrtod(trimmed, exponent, &guess)) {
     return guess;
   }
   return BignumStrtod(trimmed, exponent, guess);
 }
 
 } }  // namespace v8::internal