https://gcc.gnu.org/g:cc38bdf093c44918edff819ae6c73d03c726b341
commit r15-1256-gcc38bdf093c44918edff819ae6c73d03c726b341 Author: Jonathan Wakely <jwak...@redhat.com> Date: Tue Jun 11 11:08:12 2024 +0100 libstdc++: Improve diagnostics for invalid std::hash specializations [PR115420] When using a key type without a valid std::hash specialization the unordered containers give confusing diagnostics about the default constructor being deleted. Add a static_assert that will fail for disabled std::hash specializations (and for a subset of custom hash functions). libstdc++-v3/ChangeLog: PR libstdc++/115420 * include/bits/hashtable.h (_Hashtable): Add static_assert to check that hash function is copy constructible. * testsuite/23_containers/unordered_map/115420.cc: New test. Diff: --- libstdc++-v3/include/bits/hashtable.h | 2 ++ .../testsuite/23_containers/unordered_map/115420.cc | 16 ++++++++++++++++ 2 files changed, 18 insertions(+) diff --git a/libstdc++-v3/include/bits/hashtable.h b/libstdc++-v3/include/bits/hashtable.h index 983aa909d6c7..361da2b3b4d4 100644 --- a/libstdc++-v3/include/bits/hashtable.h +++ b/libstdc++-v3/include/bits/hashtable.h @@ -210,6 +210,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION static_assert(is_same<typename _Alloc::value_type, _Value>{}, "unordered container must have the same value_type as its allocator"); #endif + static_assert(is_copy_constructible<_Hash>::value, + "hash function must be copy constructible"); using __traits_type = _Traits; using __hash_cached = typename __traits_type::__hash_cached; diff --git a/libstdc++-v3/testsuite/23_containers/unordered_map/115420.cc b/libstdc++-v3/testsuite/23_containers/unordered_map/115420.cc new file mode 100644 index 000000000000..5528bf813bd7 --- /dev/null +++ b/libstdc++-v3/testsuite/23_containers/unordered_map/115420.cc @@ -0,0 +1,16 @@ +// { dg-do compile { target c++11 } } + +#include <unordered_map> + +struct S { }; + +void +test_pr115420() +{ + std::unordered_map<S, int> m; // { dg-error "here" } +} + +// { dg-error "hash function must be copy constructible" "" { target *-*-* } 0 } +// { dg-prune-output "use of deleted function" } +// { dg-prune-output "is private" } +// { dg-prune-output "no matching function" }