Increase precision for base conversion for large integers.

src/conversions.cc

Index: src/conversions.cc
diff --git a/src/conversions.cc b/src/conversions.cc
index 5f1219eea9139cf2aa77c0c8dda95609b6a12481..397f3c57fb8628de2e39b521ff2298dcf977db41 100644
--- a/src/conversions.cc
+++ b/src/conversions.cc
@@ -401,8 +401,9 @@ char* DoubleToRadixCString(double value, int radix) {
   // 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.