On 20/03/21 22:32 +0100, François Dumont wrote:
Following your feedback here is the simplified version. I grouped
it with the patch I submitted before.
On 19/03/21 8:41 pm, Jonathan Wakely wrote:
I think we could just define on partial specialization that works for
all cases:
Yes, sounds better. But I relied on std::__hash_base which gives
directly the correct definition.
But that is wrong.
The requirements in https://wg21.link/unord.hash say that std::hash<T>
must be disabled for unsupported types. With std::basic_string the
specialization std::hash<basic_string<int>> is disabled, because there
is no specialization for that type, so it uses the primary template of
std::hash, which is empty:
/// Primary class template hash, usable for enum types only.
// Use with non-enum types still SFINAES.
template<typename _Tp>
struct hash : __hash_enum<_Tp>
{ };
With your patch, std::hash<__gnu_debug::basic_string<int>> will not be
empty. It will provide argument_type and result_type and operator()
but calling operator() will fail to compile.
My suggestion doesn't have that problem. With my suggestion,
hash<_gnu_debug::basic_string<C>> is enabled if (and only if)
hash<std::basic_string<C>> is enabled.
libstdc++: Fix and complete __gnu_debug::basic_string implementation
Fix and complete __gnu_debug::basic_string so that it can be
used as a transparent
replacement of std::basic_string.
libstdc++-v3/ChangeLog:
* include/debug/string
(basic_string(const _CharT*, const _Allocator&)):
Remove assign call.
(basic_string<>::insert(const_iterator, _InputIte,
_InputIte)): Try to
remove iterator debug layer even if !_GLIBCXX_USE_CXX11_ABI.
[_GLIBCXX_USE_CHAR8_T] (__gnu_debug::u8string): New.
(__gnu_debug::u16string, __gnu_debug::u32string): New.
(std::hash<__gnu_debug::basic_string<>>): New partial specialization.
(std::__is_fast_hash<__gnu_debug::basic_string<>>): Likewise.
(basic_string(const basic_string&, const _Alloc&)):
Define even if !_GLIBCXX_USE_CXX11_ABI.
(basic_string(basic_string&&, const _Alloc&)):
Likewise and add noexcept qualification.
(basic_string<>::erase): Adapt to take __const_iterator.
* testsuite/21_strings/basic_string/hash/debug.cc: New test.
*
testsuite/21_strings/basic_string/hash/debug_char8_t.cc: New test.
*
testsuite/21_strings/basic_string/requirements/citerators.cc:
Adapt to test __gnu_debug::string
when _GLIBCXX_DEBUG is defined.
*
testsuite/21_strings/basic_string/requirements/dr438/constructor.cc:
Likewise.
*
testsuite/21_strings/basic_string/requirements/exception/basic.cc:
Likewise.
* testsuite/21_strings/basic_string/requirements/exception/generation_prohibited.cc:
Likewise.
* testsuite/21_strings/basic_string/requirements/exception/propagation_consistent.cc:
Likewise.
* testsuite/21_strings/basic_string/requirements/explicit_instantiation/char/1.cc:
Likewise.
* testsuite/21_strings/basic_string/requirements/explicit_instantiation/char16_t/1.cc:
Likewise.
* testsuite/21_strings/basic_string/requirements/explicit_instantiation/char32_t/1.cc:
Likewise.
* testsuite/21_strings/basic_string/requirements/explicit_instantiation/char8_t/1.cc:
Likewise.
* testsuite/21_strings/basic_string/requirements/explicit_instantiation/wchar_t/1.cc:
Likewise.
*
testsuite/21_strings/basic_string/requirements/typedefs.cc:
Likewise.
* testsuite/util/exception/safety.h
(erase_base<__gnu_debug::basic_string<>>): New partial
specialization.
(insert_base<__gnu_debug::basic_string<>>): Likewise.
* testsuite/util/testsuite_container_traits.h
(traits<__gnu_debug::basic_string<>>): Likewise.
Tested under Linux x86_64.
Ok to commit ?
François
diff --git a/libstdc++-v3/include/debug/string
b/libstdc++-v3/include/debug/string
index 172179530aa..f665c759557 100644
--- a/libstdc++-v3/include/debug/string
+++ b/libstdc++-v3/include/debug/string
@@ -41,6 +41,14 @@
__gnu_debug::_Error_formatter::_S_at(_File, _Line, _Func) \
._M_message(#_Cond)._M_error()
+#if _GLIBCXX_USE_CXX11_ABI && __cplusplus >= 201103
+# define _GLIBCXX_INSERT_RETURNS_ITERATOR 1
+# define _GLIBCXX_INSERT_RETURNS_ITERATOR_ONLY(expr) expr
+#else
+# define _GLIBCXX_INSERT_RETURNS_ITERATOR 0
+# define _GLIBCXX_INSERT_RETURNS_ITERATOR_ONLY(expr)
+#endif
+
namespace __gnu_debug
{
/** Checks that __s is non-NULL or __n == 0, and then returns __s. */
@@ -123,21 +131,21 @@ namespace __gnu_debug
using _Base::npos;
- basic_string()
- _GLIBCXX_NOEXCEPT_IF(std::is_nothrow_default_constructible<_Base>::value)
- : _Base() { }
-
// 21.3.1 construct/copy/destroy:
+
explicit
basic_string(const _Allocator& __a) _GLIBCXX_NOEXCEPT
: _Base(__a) { }
#if __cplusplus < 201103L
+ basic_string() : _Base() { }
+
basic_string(const basic_string& __str)
: _Base(__str) { }
~basic_string() { }
#else
+ basic_string() = default;
basic_string(const basic_string&) = default;
basic_string(basic_string&&) = default;
@@ -146,13 +154,15 @@ namespace __gnu_debug
: _Base(__l, __a)
{ }
-#if _GLIBCXX_USE_CXX11_ABI
basic_string(const basic_string& __s, const _Allocator& __a)
: _Base(__s, __a) { }
basic_string(basic_string&& __s, const _Allocator& __a)
- : _Base(std::move(__s), __a) { }
-#endif
+ noexcept( noexcept(
+ _Base(std::declval<_Base>()), std::declval<const _Allocator&>()) )
There is a closing ')' in the wrong place here. This checks whether
_Base is nothrow_move_constructible and whether std::declval is
nothrow.
You could just use
noexcept(is_nothrow_constructible<_Base, _Base, const
_Allocator&>::value)
or:
noexcept(noexcept(_Base(static_cast<_Base&&>(__s), __a)))
It's a bit confusing that we have a noexcept specifier that only
depends on _Base when the _Safe base class can also throw:
+ : _Safe(std::move(__s._M_safe()), __a),
+ _Base(std::move(__s._M_base()), __a)
+ { }
In fact, it is conditionally noexcept with the same condition as the
_Base type, so checking if the _Base construction is non-throwing is
correct. But confusing.
+ /// std::hash specialization for __gnu_debug::basic_string.
+ template<typename _CharT>
+ struct hash<__gnu_debug::basic_string<_CharT>>
+ : public __hash_base<size_t, __gnu_debug::basic_string<_CharT>>
+ {
+ size_t
+ operator()(const __gnu_debug::basic_string<_CharT>& __s)
const noexcept
+ { return std::hash<std::basic_string<_CharT>>()(__s); }
+ };
+
+ template<typename _CharT>
+ struct __is_fast_hash<hash<__gnu_debug::basic_string<_CharT>>>
+ : std::false_type
This says it's always a slow hash, rather than deferring to
__is_fast_hash<hash<std::basic_string<C>>>.
That means __is_fast_hash is false for __gnu_debug::basic_string<int>
but true for std::basic_string<int>. In practice it probably doesn't
matter, but it's inconsistent.
+ { };
+
+_GLIBCXX_END_NAMESPACE_VERSION
+}
+#endif /* C++11 */
+
+#undef _GLIBCXX_INSERT_RETURNS_ITERATOR
+#undef _GLIBCXX_INSERT_RETURNS_ITERATOR_ONLY
+
#endif
diff --git
a/libstdc++-v3/testsuite/21_strings/basic_string/hash/debug.cc
b/libstdc++-v3/testsuite/21_strings/basic_string/hash/debug.cc
new file mode 100644
index 00000000000..84c989590b7
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/hash/debug.cc
@@ -0,0 +1,53 @@
+// Copyright (C) 2021 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library. This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public
License along
+// with this library; see the file COPYING3. If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++17" }
+// { dg-do run { target c++17 } }
-std=gnu++17 is the default now, so should not be given explicitly.
You could combine this test and debug/hash_char8_t.cc by adding the
char8_t parts guarded by _GLIBCXX_USE_CHAR8_T. When the test is run
with a -std=gnu++20 it will test the char8_t parts (which is why we
don't want the redundant -std=gnu++17, because it would prevent it
from being run with -std=gnu++20).
diff --git
a/libstdc++-v3/testsuite/21_strings/basic_string/requirements/citerators.cc
b/libstdc++-v3/testsuite/21_strings/basic_string/requirements/citerators.cc
index 99bf5726dcc..69d4a8d0e51 100644
--- a/libstdc++-v3/testsuite/21_strings/basic_string/requirements/citerators.cc
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/requirements/citerators.cc
@@ -18,14 +18,21 @@
// with this library; see the file COPYING3. If not see
// <http://www.gnu.org/licenses/>.
-#include <string>
#include <testsuite_containers.h>
+#ifdef _GLIBCXX_DEBUG
+# include <debug/string>
+using namespace __gnu_debug;
+#else
+# include <string>
+using namespace std;
+#endif
This has the same problem I pointed out previously. With this change,
we don't run this test for std::string in debug mode. When debug
mode is active, we test a different type not std::string.
That means if we introduce a bug to std::string that only affects
debug mode, we might not notice, because we're stopped testing
std::string in debug mode.
If you want to test __gnu_debug::basic_string then those tests should
be added as new tests, not by replacing existing tests that are
already testing something different.
