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author | Jonathan Wakely <jwakely@redhat.com> | 2022-08-24 00:10:59 +0100 |
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committer | Jonathan Wakely <jwakely@redhat.com> | 2022-08-24 12:27:51 +0100 |
commit | f0f04e1dffea609cb74ac0b488385401ed7e15a3 (patch) | |
tree | c0b52c14c2878b85dc0946baf03645d2bd3cdb99 | |
parent | 4a907b15b551becd3145061a8906089267db5a04 (diff) | |
download | gcc-f0f04e1dffea609cb74ac0b488385401ed7e15a3.zip gcc-f0f04e1dffea609cb74ac0b488385401ed7e15a3.tar.gz gcc-f0f04e1dffea609cb74ac0b488385401ed7e15a3.tar.bz2 |
libstdc++: Add check for LWG 3741 problem case
This LWG issue was closed as NAD, as it was just a bug in an
implementation, not a defect in the standard. Libstdc++ never had that
bug and always worked for the problem case. Add a test to ensure we
don't regress.
The problem occurs when abs is implemented using a ternary expression:
return d >= d.zero() ? d : -d;
If decltype(-d) is not the same as decltype(d) then this is ambiguous,
because each type can be converted to the other, so there is no common
type.
libstdc++-v3/ChangeLog:
* testsuite/20_util/duration_cast/rounding.cc: Check abs with
non-reduced duration.
-rw-r--r-- | libstdc++-v3/testsuite/20_util/duration_cast/rounding.cc | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/libstdc++-v3/testsuite/20_util/duration_cast/rounding.cc b/libstdc++-v3/testsuite/20_util/duration_cast/rounding.cc index af6e72d..c5179b6 100644 --- a/libstdc++-v3/testsuite/20_util/duration_cast/rounding.cc +++ b/libstdc++-v3/testsuite/20_util/duration_cast/rounding.cc @@ -58,3 +58,8 @@ static_assert( std::chrono::round<seconds>(2501ms) == 3s ); static_assert( std::chrono::abs(100ms) == 100ms ); static_assert( std::chrono::abs(-100ms) == 100ms ); + +// LWG 3741. std::chrono::abs(duration) is ill-formed with non-reduced periods +using D1000 = std::chrono::duration<int, std::ratio<1000, 1000>>; +static_assert( std::chrono::abs(D1000(-2)) == D1000(2) ); +static_assert( std::is_same_v<decltype(std::chrono::abs(D1000(-2))), D1000> ); |