On 02/05/19 21:33 +0100, Jonathan Wakely wrote:
On 02/05/19 20:11 +0100, Jonathan Wakely wrote:
On 02/05/19 20:09 +0100, Jonathan Wakely wrote:
On 02/05/19 20:34 +0200, Stephan Bergmann wrote:
On 29/04/2019 15:26, Jonathan Wakely wrote:
* include/bits/move.h (swap(T&, T&), swap(T (&)[N], T (&)[N])): Use
_GLIBCXX_NOEXCEPT_IF to simplify declarations.
This just avoids having to repeat the name and parameter-list of the
functions.
libstdc++-v3/include/std/type_traits still has
template<typename _Tp>
inline
typename enable_if<__and_<__not_<__is_tuple_like<_Tp>>,
is_move_constructible<_Tp>,
is_move_assignable<_Tp>>::value>::type
swap(_Tp&, _Tp&)
noexcept(__and_<is_nothrow_move_constructible<_Tp>,
is_nothrow_move_assignable<_Tp>>::value);
using noexcept instead of _GLIBCXX_NOEXPECT_IF, and at least
during configure of building LibreOffice with Clang, that causes
failure
.../gcc/trunk/lib/gcc/x86_64-pc-linux-gnu/10.0.0/../../../../include/c++/10.0.0/bits/move.h:185:5:
error: exception specification in declaration does not match previous
declaration
swap(_Tp& __a, _Tp& __b)
^
.../gcc/trunk/lib/gcc/x86_64-pc-linux-gnu/10.0.0/../../../../include/c++/10.0.0/type_traits:2531:5:
note: previous declaration is here
swap(_Tp&, _Tp&)
^
I didn't try to track down under what conditions
_GLIBCXX_NOEXCEPT_IF would not expand to noexcept, but I assume
that just type_traits needs adapting, too?
That's weird. _GLIBCXX_NOEXCEPT_IF is only empty for C++11, in which
case the declaration in <type_traits> isn't seen anyway. And there's
no point using _GLIBCXX_NOEXCEPT_IF in <type_traits> because we can
(and should) just use noexcept directly in C++11 code. The macro
exists for code that needs to be compiled as C++98 too.
The only difference is that there's an extra set of parentheses around
the NOEXCEPT_IF condition, so the preprocessor doesn't try to eat the
comma.
So one declaration is:
template<typename _Tp>
inline
typename enable_if<__and_<__not_<__is_tuple_like<_Tp>>,
is_move_constructible<_Tp>,
is_move_assignable<_Tp>>::value>::type
swap(_Tp&, _Tp&)
noexcept(__and_<is_nothrow_move_constructible<_Tp>,
is_nothrow_move_assignable<_Tp>>::value);
And the other is:
template<typename _Tp>
inline
typename enable_if<__and_<__not_<__is_tuple_like<_Tp>>,
is_move_constructible<_Tp>,
is_move_assignable<_Tp>>::value>::type
swap(_Tp&, _Tp&)
noexcept((__and_<is_nothrow_move_constructible<_Tp>,
is_nothrow_move_assignable<_Tp>>::value));
Yep, Clang doesn't like that:
https://wandbox.org/permlink/clslE9PGCVtKPppz
This was also reported as https://gcc.gnu.org/PR90314
And here's what I've tested and committed.
commit 3a40e123af3226cd577de7db678fff5815816487
Author: Jonathan Wakely <jwak...@redhat.com>
Date: Thu May 2 21:52:09 2019 +0100
PR libstdc++/90314 fix non-equivalent declarations of std::swap
In order to use the _GLIBCXX_NOEXCEPT_IF macro for an expression
containing commas I enclosed it in parentheses, so the preprocessor
wouldn't treat it as two arguments to the function-like macro. Clang
gives an error because now the noexcept-specifier noexcept((C)) is not
equivalent to the noexcept(C) one on the declaration of swap in
<type_traits>.
Instead of requiring extra parentheses around the expression, redefine
_GLIBCXX_NOEXCEPT_IF as a variadic macro (even though supporting that in
C++98 is a GNU extension).
PR libstdc++/90314
* include/bits/c++config (_GLIBCXX_NOEXCEPT_IF): Use variadic macro.
* include/bits/move.h (swap): Remove extra parentheses.
diff --git a/libstdc++-v3/include/bits/c++config b/libstdc++-v3/include/bits/c++config
index 5016f4853de..ca1557af564 100644
--- a/libstdc++-v3/include/bits/c++config
+++ b/libstdc++-v3/include/bits/c++config
@@ -157,12 +157,12 @@
#ifndef _GLIBCXX_NOEXCEPT
# if __cplusplus >= 201103L
# define _GLIBCXX_NOEXCEPT noexcept
-# define _GLIBCXX_NOEXCEPT_IF(_COND) noexcept(_COND)
+# define _GLIBCXX_NOEXCEPT_IF(...) noexcept(__VA_ARGS__)
# define _GLIBCXX_USE_NOEXCEPT noexcept
# define _GLIBCXX_THROW(_EXC)
# else
# define _GLIBCXX_NOEXCEPT
-# define _GLIBCXX_NOEXCEPT_IF(_COND)
+# define _GLIBCXX_NOEXCEPT_IF(...)
# define _GLIBCXX_USE_NOEXCEPT throw()
# define _GLIBCXX_THROW(_EXC) throw(_EXC)
# endif
diff --git a/libstdc++-v3/include/bits/move.h b/libstdc++-v3/include/bits/move.h
index 996078cfbce..7271e273e8e 100644
--- a/libstdc++-v3/include/bits/move.h
+++ b/libstdc++-v3/include/bits/move.h
@@ -183,8 +183,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
void
#endif
swap(_Tp& __a, _Tp& __b)
- _GLIBCXX_NOEXCEPT_IF((__and_<is_nothrow_move_constructible<_Tp>,
- is_nothrow_move_assignable<_Tp>>::value))
+ _GLIBCXX_NOEXCEPT_IF(__and_<is_nothrow_move_constructible<_Tp>,
+ is_nothrow_move_assignable<_Tp>>::value)
{
// concept requirements
__glibcxx_function_requires(_SGIAssignableConcept<_Tp>)
