Remove the try/catch codepath if `swap` is `noexcept`.
Summary:
In the case where `swap` is `noexcept`, we should avoid the extension to provide strong-exception guarantee.
Fixes https://bugs.llvm.org/show_bug.cgi?id=46342
Reviewers: #libc, ldionne
Reviewed By: #libc, ldionne
Subscribers: dexonsmith, mclow.lists, miscco, ldionne, zoecarver, libcxx-commits
Tags: #libc
Differential Revision: https://reviews.llvm.org/D81954
Cr-Mirrored-From: https://chromium.googlesource.com/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: ada2a8ea4a9c5b2141c30c77b80b85945e346999
diff --git a/include/variant b/include/variant
index 98a62c9..897361f 100644
--- a/include/variant
+++ b/include/variant
@@ -1062,21 +1062,28 @@
_VSTD::swap(__lhs, __rhs);
}
__impl __tmp(_VSTD::move(*__rhs));
-#ifndef _LIBCPP_NO_EXCEPTIONS
- // EXTENSION: When the move construction of `__lhs` into `__rhs` throws
- // and `__tmp` is nothrow move constructible then we move `__tmp` back
- // into `__rhs` and provide the strong exception safety guarantee.
- try {
- this->__generic_construct(*__rhs, _VSTD::move(*__lhs));
- } catch (...) {
- if (__tmp.__move_nothrow()) {
- this->__generic_construct(*__rhs, _VSTD::move(__tmp));
- }
- throw;
- }
+ static constexpr bool __is_noexcept =
+#ifdef _LIBCPP_NO_EXCEPTIONS
+ true;
#else
- this->__generic_construct(*__rhs, _VSTD::move(*__lhs));
+ __all<(is_nothrow_move_constructible_v<_Types> &&
+ is_nothrow_swappable_v<_Types>)...>::value;
#endif
+ if constexpr (__is_noexcept) {
+ this->__generic_construct(*__rhs, _VSTD::move(*__lhs));
+ } else {
+ // EXTENSION: When the move construction of `__lhs` into `__rhs` throws
+ // and `__tmp` is nothrow move constructible then we move `__tmp` back
+ // into `__rhs` and provide the strong exception safety guarantee.
+ try {
+ this->__generic_construct(*__rhs, _VSTD::move(*__lhs));
+ } catch (...) {
+ if (__tmp.__move_nothrow()) {
+ this->__generic_construct(*__rhs, _VSTD::move(__tmp));
+ }
+ throw;
+ }
+ }
this->__generic_construct(*__lhs, _VSTD::move(__tmp));
}
}