Re: [PATCH] Use __is_same_as for std::is_same and std::is_same_v

[Romain Geissler <romain dot geissler at gmail dot com>]

Le ven. 11 oct. 2019 à 17:50, Jonathan Wakely <jwakely@redhat.com> a écrit :
>
> By using the built-in we don't need to match a partial specialization
> for std::is_same and don't need to instantiate std::is_same at all for
> uses of std::is_same_v.
>
>         * include/std/type_traits (is_same): Replace partial specialization
>         by using __is_same_as built-in in primary template.
>         (is_same_v): Use __is_same_as built-in instead of instantiating the
>         is_same trait.
>
> Tested x86_64-linux, committed to trunk.
>

Hi Jonathan,

It looks like this creates the following error when I try to bootstrap
clang 9.0.0 using the latest gcc and libstdc++ from trunk. Note that
with g++, there is no problem, however it looks like clang++ has some
problem with the new header. I don't know if this is an issue on
libstdc++ side or clang++ side.

Cheers,
Romain

FAILED: compiler-rt/lib/xray/CMakeFiles/RTXray.x86_64.dir/xray_buffer_queue.cc.o
/workdir/build/final-system/llvm-build/./bin/clang++
--target=x86_64-1a-linux-gnu  -DXRAY_HAS_EXCEPTIONS=1
-D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS
-I/workdir/src/llvm-9.0.0/compiler-rt/lib/xray/..
-I/workdir/src/llvm-9.0.0/compiler-rt/lib/xray/../../include -O2 -msse
-msse2 -msse3 -I/workdir/build/final-system/llvm-temporary-static-dependencies/install/include
-I/workdir/build/final-system/llvm-temporary-static-dependencies/install/include/ncursesw
-fvisibility-inlines-hidden -Werror=date-time
-Werror=unguarded-availability-new -std=c++11 -Wall -Wextra
-Wno-unused-parameter -Wwrite-strings -Wcast-qual
-Wmissing-field-initializers -Wimplicit-fallthrough
-Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor
-Wdelete-non-virtual-dtor -Wstring-conversion -fdiagnostics-color
-ffunction-sections -fdata-sections -Wall -std=c++11
-Wno-unused-parameter -O3 -DNDEBUG    -m64 -fPIC -fno-builtin
-fno-exceptions -fomit-frame-pointer -funwind-tables
-fno-stack-protector -fno-sanitize=safe-stack -fvisibility=hidden
-fno-lto -O3 -gline-tables-only -Wno-gnu -Wno-variadic-macros
-Wno-c99-extensions -Wno-non-virtual-dtor -fno-rtti -MD -MT
compiler-rt/lib/xray/CMakeFiles/RTXray.x86_64.dir/xray_buffer_queue.cc.o
-MF compiler-rt/lib/xray/CMakeFiles/RTXray.x86_64.dir/xray_buffer_queue.cc.o.d
-o compiler-rt/lib/xray/CMakeFiles/RTXray.x86_64.dir/xray_buffer_queue.cc.o
-c /workdir/src/llvm-9.0.0/compiler-rt/lib/xray/xray_buffer_queue.cc
In file included from
/workdir/src/llvm-9.0.0/compiler-rt/lib/xray/xray_buffer_queue.cc:21:
In file included from
/workdir/src/llvm-9.0.0/compiler-rt/lib/xray/xray_allocator.h:29:
In file included from
/workdir/src/llvm-9.0.0/compiler-rt/lib/xray/xray_utils.h:20:
In file included from
/opt/1A/toolchain/x86_64-v20.0.3/lib64/gcc/x86_64-1a-linux-gnu/10.0.0/../../../../include/c++/10.0.0/utility:70:
In file included from
/opt/1A/toolchain/x86_64-v20.0.3/lib64/gcc/x86_64-1a-linux-gnu/10.0.0/../../../../include/c++/10.0.0/bits/stl_pair.h:59:
In file included from
/opt/1A/toolchain/x86_64-v20.0.3/lib64/gcc/x86_64-1a-linux-gnu/10.0.0/../../../../include/c++/10.0.0/bits/move.h:55:
/opt/1A/toolchain/x86_64-v20.0.3/lib64/gcc/x86_64-1a-linux-gnu/10.0.0/../../../../include/c++/10.0.0/type_traits:1393:51:
error: '_Tp' does not refer to a value
    : public integral_constant<bool, __is_same_as(_Tp, _Up)>
                                                  ^
/opt/1A/toolchain/x86_64-v20.0.3/lib64/gcc/x86_64-1a-linux-gnu/10.0.0/../../../../include/c++/10.0.0/type_traits:1391:21:
note: declared here
  template<typename _Tp, typename _Up>
                    ^
/opt/1A/toolchain/x86_64-v20.0.3/lib64/gcc/x86_64-1a-linux-gnu/10.0.0/../../../../include/c++/10.0.0/type_traits:1393:56:
error: '_Up' does not refer to a value
    : public integral_constant<bool, __is_same_as(_Tp, _Up)>
                                                       ^
/opt/1A/toolchain/x86_64-v20.0.3/lib64/gcc/x86_64-1a-linux-gnu/10.0.0/../../../../include/c++/10.0.0/type_traits:1391:35:
note: declared here
  template<typename _Tp, typename _Up>
                                  ^
2 errors generated.