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Improve diagnostics when an invalid hash is used in an unordered container.

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This patch adds a static assertion that the specified hash meets
the requirements of an enabled hash, and it ensures that the static
assertion is evaluated before __compressed_pair is instantiated.
That way the static assertion diagnostic is emitted first.

llvm-svn: 296565
This commit is contained in:
Eric Fiselier 2017-03-01 02:02:28 +00:00
parent 65f8cf945d
commit acb21581d7
2 changed files with 52 additions and 7 deletions
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27
libcxx/include/__hash_table
View File

@ -871,11 +871,20 @@ public:
template <class _Key, class _Hash, class _Equal, class _Alloc>
struct __diagnose_hash_table_helper {
static constexpr bool __trigger_diagnostics()
_LIBCPP_DIAGNOSE_WARNING(!__invokable<_Hash const&, _Key const&>::value,
"the specified hash functor does not provide a const call operator")
_LIBCPP_DIAGNOSE_WARNING(!__invokable<_Equal const&, _Key const&, _Key const&>::value,
"the specified comparator type does not provide a const call operator")
{ return true; }
_LIBCPP_DIAGNOSE_WARNING(__has_enabled_hash<_Key, _Hash>::value
&& !__invokable<_Hash const&, _Key const&>::value,
"the specified hash functor does not provide a const call operator")
_LIBCPP_DIAGNOSE_WARNING(is_copy_constructible<_Equal>::value
&& !__invokable<_Equal const&, _Key const&, _Key const&>::value,
"the specified comparator type does not provide a const call operator")
{
static_assert(__has_enabled_hash<_Key, _Hash>::value,
"the specified hash functor does not meet the requirements for an "
"enabled hash");
static_assert(is_copy_constructible<_Equal>::value,
"the specified comparator is required to be copy constructible");
return true;
}
};
template <class _Key, class _Value, class _Hash, class _Equal, class _Alloc>
@ -951,6 +960,10 @@ private:
typedef allocator_traits<__pointer_allocator> __pointer_alloc_traits;
typedef typename __bucket_list_deleter::pointer __node_pointer_pointer;
#ifndef _LIBCPP_CXX03_LANG
static_assert(__diagnose_hash_table_helper<_Tp, _Hash, _Equal, _Alloc>::__trigger_diagnostics(), "");
#endif
// --- Member data begin ---
__bucket_list __bucket_list_;
__compressed_pair<__first_node, __node_allocator> __p1_;
@ -1482,13 +1495,13 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__hash_table(__hash_table&& __u,
template <class _Tp, class _Hash, class _Equal, class _Alloc>
__hash_table<_Tp, _Hash, _Equal, _Alloc>::~__hash_table()
{
#if defined(_LIBCPP_CXX03_LANG)
static_assert((is_copy_constructible<key_equal>::value),
"Predicate must be copy-constructible.");
static_assert((is_copy_constructible<hasher>::value),
"Hasher must be copy-constructible.");
#ifndef _LIBCPP_CXX03_LANG
static_assert(__diagnose_hash_table_helper<_Tp, _Hash, _Equal, _Alloc>::__trigger_diagnostics(), "");
#endif
__deallocate_node(__p1_.first().__next_);
#if _LIBCPP_DEBUG_LEVEL >= 2
__get_db()->__erase_c(this);

32
libcxx/test/libcxx/containers/unord/unord.set/missing_hash_specialization.fail.cpp Normal file
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@ -0,0 +1,32 @@
//===----------------------------------------------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
// UNSUPPORTED: c++98, c++03
// REQUIRES: diagnose-if-support
// <unordered_set>
// Test that we generate a reasonable diagnostic when the specified hash is
// not enabled.
#include <unordered_set>
#include <utility>
using VT = std::pair<int, int>;
using Set = std::unordered_set<VT>;
int main() {
Set s; // expected-error@__hash_table:* {{the specified hash functor does not meet the requirements for an enabled hash}}
// FIXME: It would be great to suppress the below diagnostic all together.
// but for now it's sufficient that it appears last. However there is
// currently no way to test the order diagnostics are issued.
// expected-error@memory:* {{call to implicitly-deleted default constructor of 'std::__1::hash<std::__1::pair<int, int> >'}}
}