Increase precision for base conversion for large integers.

src/conversions.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 383 matching lines @@
   if (is_negative) value = -value;
 
   // Get the integer part and the decimal part.
   double integer_part = floor(value);
   double decimal_part = value - integer_part;
 
   // Convert the integer part starting from the back.  Always generate
   // at least one digit.
   int integer_pos = kBufferSize - 2;
   do {
-    integer_buffer[integer_pos--] =
-        chars[static_cast<int>(fmod(integer_part, radix))];
+    double remainder = fmod(integer_part, radix);
+    integer_buffer[integer_pos--] = chars[static_cast<int>(remainder)];
+    integer_part -= remainder;
     integer_part /= radix;
   } while (integer_part >= 1.0);
   // Sanity check.
   ASSERT(integer_pos > 0);
   // Add sign if needed.
   if (is_negative) integer_buffer[integer_pos--] = '-';
 
   // Convert the decimal part.  Repeatedly multiply by the radix to
   // generate the next char.  Never generate more than kBufferSize - 1
   // chars.
@@ skipping 20 matching lines @@
   if (decimal_pos > 0) result_size++;
   // Allocate result and fill in the parts.
   SimpleStringBuilder builder(result_size + 1);
   builder.AddSubstring(integer_buffer + integer_pos + 1, integer_part_size);
   if (decimal_pos > 0) builder.AddCharacter('.');
   builder.AddSubstring(decimal_buffer, decimal_pos);
   return builder.Finalize();
 }
 
 } }  // namespace v8::internal