Fix dragonbox integration

include/fmt/format-inl.h

@@ -2307,6 +2307,10 @@ FMT_SAFEBUFFERS decimal_fp<T> to_decimal(T x) FMT_NOEXCEPT {
       goto small_divisor_case_label;
     }
   }
+  if (ret_value.significand == 0) {
+    ret_value.exponent = 0;
+    return ret_value;
+  }
   ret_value.exponent = minus_k + float_info<T>::kappa + 1;
 
   // We may need to remove trailing zeros

test/format-test.cc

@@ -1238,10 +1238,12 @@ TEST(FormatterTest, FormatConvertibleToLongLong) {
 }
 
 TEST(FormatterTest, FormatFloat) {
+  EXPECT_EQ("0", format("{}", 0.0f));
   EXPECT_EQ("392.500000", format("{0:f}", 392.5f));
 }
 
 TEST(FormatterTest, FormatDouble) {
+  EXPECT_EQ("0", format("{}", 0.0));
   check_unknown_types(1.2, "eEfFgGaAnL%", "double");
   EXPECT_EQ("0", format("{:}", 0.0));
   EXPECT_EQ("0.000000", format("{:f}", 0.0));