From 434e30f81f8735d4c629acea485e6bb3e059e937 Mon Sep 17 00:00:00 2001
From: Mohith <122464960+MokiMeow@users.noreply.github.com>
Date: Sat, 24 Oct 2026 22:58:23 +0530
Subject: [PATCH] Fix signs in floating-point duration formatting (#4981)

---
 include/fmt/chrono.h |  8 +++-----
 test/chrono-test.cc  | 29 +++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 5 deletions(-)

diff --git a/include/fmt/chrono.h b/include/fmt/chrono.h
index c0b88b3c..62f84b6e 100644
--- a/include/fmt/chrono.h
+++ b/include/fmt/chrono.h
@@ -1687,10 +1687,8 @@ struct duration_formatter {
       return true;
     }
     // must be +-inf
-    if (val > 0)
-      std::copy_n("inf", 3, out);
-    else
-      std::copy_n("-inf", 4, out);
+    write_sign();
+    std::copy_n("inf", 3, out);
     return true;
   }
 
@@ -1815,7 +1813,7 @@ struct duration_formatter {
         auto buf = memory_buffer();
         write_floating_seconds(buf, std::chrono::duration<rep, Period>(val),
                                precision);
-        if (negative) *out++ = '-';
+        write_sign();
         if (buf.size() < 2 || buf[1] == '.')
           out = detail::write_padding(out, pad);
         out = copy<Char>(buf.begin(), buf.end(), out);
diff --git a/test/chrono-test.cc b/test/chrono-test.cc
index a2f419ad..f7010943 100644
--- a/test/chrono-test.cc
+++ b/test/chrono-test.cc
@@ -755,6 +755,35 @@ TEST(chrono_test, special_durations) {
       "01.234");
 }
 
+TEST(chrono_test, negative_floating_duration_sign) {
+  auto d = std::chrono::duration<double>(-61.25);
+  EXPECT_EQ(fmt::format("{:%S %M}", d), "-01.250000 01");
+  EXPECT_EQ(fmt::format("{:%S %S}", d), "-01.250000 01.250000");
+  EXPECT_EQ(fmt::format("{:%S %Q}", d), "-01.250000 61.25");
+  EXPECT_EQ(fmt::format("{:%Q %S}", d), "-61.25 01.250000");
+  EXPECT_EQ(fmt::format("{:%S %Q}", -d), "01.250000 61.25");
+  EXPECT_EQ(fmt::format("{:%S %Q}", std::chrono::duration<float>(-1)), "-01 1");
+  EXPECT_EQ(fmt::format("{:%S %Q}", std::chrono::duration<long double>(-1)),
+            "-01 1");
+}
+
+TEST(chrono_test, negative_infinite_duration_sign) {
+  auto inf = std::numeric_limits<double>::infinity();
+  auto d = std::chrono::duration<double>(-inf);
+  EXPECT_EQ(fmt::format("{:%Q}", d), "-inf");
+  EXPECT_EQ(fmt::format("{:%S}", d), "-inf");
+  EXPECT_EQ(fmt::format("{:%H}", d), "-inf");
+  EXPECT_EQ(fmt::format("{:%j}", d), "-inf");
+  EXPECT_EQ(fmt::format("{:%R}", d), "-inf:inf");
+  EXPECT_EQ(fmt::format("{:%T}", d), "-inf:inf:inf");
+  EXPECT_EQ(fmt::format("{:%S %Q}", d), "-inf inf");
+  EXPECT_EQ(fmt::format("{:>6%Q}", d), "  -inf");
+  EXPECT_EQ(fmt::format("{:%Q %S}", -d), "inf inf");
+  EXPECT_EQ(fmt::format("{:%Q}", std::chrono::duration<float>(-inf)), "-inf");
+  EXPECT_EQ(fmt::format("{:%Q}", std::chrono::duration<long double>(-inf)),
+            "-inf");
+}
+
 TEST(chrono_test, unsigned_duration) {
   EXPECT_EQ(fmt::format("{}", std::chrono::duration<unsigned>(42)), "42s");
 }