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From: Benjamin Barenblat <bbaren@google.com>
Subject: Avoid libgcc -NaN narrowing bug
Forwarded: yes
Applied-Upstream: https://github.com/abseil/abseil-cpp/commit/1bae23e32ba1f1af7c7d1488a69a351ec96dc98d
When testing -NaN parsing, avoid narrowing -NaN from double to float. This
avoids a bug in libgcc (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98251).
The author works at Google. Upstream applied this patch as Piper revision
347654751 and exported it to GitHub; the Applied-Upstream URL above points to
the exported commit.
--- a/absl/strings/charconv_test.cc
+++ b/absl/strings/charconv_test.cc
@@ -653,7 +653,9 @@ TEST(FromChars, NaNFloats) {
negative_from_chars_float);
EXPECT_TRUE(std::signbit(negative_from_chars_float));
EXPECT_FALSE(Identical(negative_from_chars_float, from_chars_float));
- from_chars_float = std::copysign(from_chars_float, -1.0);
+ // Use the (float, float) overload of std::copysign to prevent narrowing;
+ // see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98251.
+ from_chars_float = std::copysign(from_chars_float, -1.0f);
EXPECT_TRUE(Identical(negative_from_chars_float, from_chars_float));
}
}
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