Fix fixed rounding around zero in Dragon

fmtlib · Feb 3, 2024 · 06311ed · 06311ed
1 parent e5bab8d
commit 06311ed
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Showing 2 changed files with 8 additions and 2 deletions.
diff --git a/include/fmt/format.h b/include/fmt/format.h
@@ -3104,8 +3104,11 @@ FMT_CONSTEXPR20 inline void format_dragon(basic_fp<uint128_t> value,
   // Generate the given number of digits.
   exp10 -= num_digits - 1;
   if (num_digits <= 0) {
-    denominator *= 10;
-    auto digit = add_compare(numerator, numerator, denominator) > 0 ? '1' : '0';
+    auto digit = '0';
+    if (num_digits == 0) {
+      denominator *= 10;
+      digit = add_compare(numerator, numerator, denominator) > 0 ? '1' : '0';
+    }
     buf.push_back(digit);
     return;
   }

diff --git a/test/format-test.cc b/test/format-test.cc
@@ -953,6 +953,9 @@ TEST(format_test, precision) {
   EXPECT_EQ(fmt::format("{0:.3}", 1.1), "1.1");
   EXPECT_EQ(fmt::format("{:.0e}", 1.0L), "1e+00");
   EXPECT_EQ(fmt::format("{:9.1e}", 0.0), "  0.0e+00");
+  EXPECT_EQ(fmt::format("{:.7f}", 0.0000000000000071054273576010018587L),
+            "0.0000000");
+
   EXPECT_EQ(
       fmt::format("{:.494}", 4.9406564584124654E-324),
       "4.9406564584124654417656879286822137236505980261432476442558568250067550"