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| author | Jonathan Wakely <jwakely@redhat.com> | 2024-06-18 16:59:52 +0100 |
|---|---|---|
| committer | Jonathan Wakely <jwakely@redhat.com> | 2024-06-21 10:19:35 +0100 |
| commit | 466ee78e3e975627440992dac67973ee314a0551 (patch) | |
| tree | 778479b8c610c9ad2c1e11d651cfd4fabc601ab8 | |
| parent | c3e237338eb7ffc90f3cc8d32a3971d17f6d0b31 (diff) | |
| download | gcc-466ee78e3e975627440992dac67973ee314a0551.zip gcc-466ee78e3e975627440992dac67973ee314a0551.tar.gz gcc-466ee78e3e975627440992dac67973ee314a0551.tar.bz2 | |
libstdc++: Make std::any_cast<void> ill-formed (LWG 3305)
LWG 3305 was approved earlier this year in Tokyo. We need to give an
error if using std::any_cast<void>, but std::any_cast<void()> is valid
(but always returns null).
libstdc++-v3/ChangeLog:
* include/std/any (any_cast(any*), any_cast(const any*)): Add
static assertion to reject void types, as per LWG 3305.
* testsuite/20_util/any/misc/lwg3305.cc: New test.
| -rw-r--r-- | libstdc++-v3/include/std/any | 8 | ||||
| -rw-r--r-- | libstdc++-v3/testsuite/20_util/any/misc/lwg3305.cc | 15 |
2 files changed, 23 insertions, 0 deletions
diff --git a/libstdc++-v3/include/std/any b/libstdc++-v3/include/std/any index 690ddc2..e4709b1c 100644 --- a/libstdc++-v3/include/std/any +++ b/libstdc++-v3/include/std/any @@ -554,6 +554,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION template<typename _ValueType> inline const _ValueType* any_cast(const any* __any) noexcept { + // _GLIBCXX_RESOLVE_LIB_DEFECTS + // 3305. any_cast<void> + static_assert(!is_void_v<_ValueType>); + + // As an optimization, don't bother instantiating __any_caster for + // function types, since std::any can only hold objects. if constexpr (is_object_v<_ValueType>) if (__any) return static_cast<_ValueType*>(__any_caster<_ValueType>(__any)); @@ -563,6 +569,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION template<typename _ValueType> inline _ValueType* any_cast(any* __any) noexcept { + static_assert(!is_void_v<_ValueType>); + if constexpr (is_object_v<_ValueType>) if (__any) return static_cast<_ValueType*>(__any_caster<_ValueType>(__any)); diff --git a/libstdc++-v3/testsuite/20_util/any/misc/lwg3305.cc b/libstdc++-v3/testsuite/20_util/any/misc/lwg3305.cc new file mode 100644 index 0000000..49f5d74 --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/any/misc/lwg3305.cc @@ -0,0 +1,15 @@ +// { dg-do compile { target c++17 } } + +// LWG 3305. any_cast<void> + +#include <any> + +void +test_lwg3305() +{ + std::any a; + (void) std::any_cast<const void>(&a); // { dg-error "here" } + const std::any a2; + (void) std::any_cast<volatile void>(&a2); // { dg-error "here" } +} +// { dg-error "static assertion failed" "" { target *-*-* } 0 } |