[cfe-dev] Unexpected check-libcxx failures on FreeBSD
Eric Fiselier via cfe-dev
cfe-dev at lists.llvm.org
Fri Oct 7 19:11:41 PDT 2016
On second thought applying (A) might be ill-advised. Most of the pair tests
still fail after applying it in constructs like
"std::is_copy_constructible_v<std::pair<NonCopyable, int&&>>", except now
instead of returning the wrong answer the traits cause hard compile errors
and template barf.
@Ed, David, and Dimitry The FreeBSD std::pair implementation is
fundamentally broken, and there's not much I think I can do about it. Is
there a timeline for making the ABI change in FreeBSD?
/Eric
On Fri, Oct 7, 2016 at 7:59 PM, Eric Fiselier <eric at efcs.ca> wrote:
> > Does anyone know what the problem may be?
>
> FreeBSD ships std::pair with explicitly defined copy and move constructors
> as opposed to explicitly defaulted ones. Mistakenly these constructors have
> not been marked constexpr in C++14.
> FreeBSD provides these old constructors is because switching to defaulted
> copy/move constructors is an ABI break because it makes std::pair
> non-trivial and changes how it's passed to functions according to the
> Itanium ABI.
>
> Fixing this requires either (A) marking the fallback constructors
> constexpr in C++14, or (B) convincing FreeBSD to take the ABI break.
>
> The easiest and simplistic fix is (A). However my concern with (A) is that
> the fallback constructors don't SFINAE away if they are ill-formed. This
> means that applying constexpr to them could break existing code by causing
> the eager instantiation of the ill-formed constructors, instantiations that
> would not occur if the constructors were non-constexpr. For this reason I
> think fix (B) is more correct, and greatly preferable.
>
> Since we have plenty of time until the next release I'll go ahead and
> commit (A) for now, keeping my ear to the ground for breakage.
>
> /Eric
>
>
> On Fri, Oct 7, 2016 at 7:23 PM, Krzysztof Parzyszek via cfe-dev <
> cfe-dev at lists.llvm.org> wrote:
>
>> I'm running this on FreeBSD 11 (stable). It has clang-3.8.0 as the system
>> compiler. LLVM/Clang/et al. compiled without problems, but I'm seeing
>> failures in check-libcxx. Example below.
>>
>> Does anyone know what the problem may be?
>>
>>
>> clang version 4.0.0 (http://llvm.org/git/clang.git
>> a85c03256cfc0812e268f5e0f1b804910e75e673) (http://llvm.org/git/llvm.git
>> c95d4ff692323bde64fc8ef45e174b19450779af)
>> Target: x86_64-unknown-freebsd11.0
>> Thread model: posix
>> InstalledDir: /w/c/org/bin
>> "/w/c/org/bin/clang-4.0" -cc1 -triple x86_64-unknown-freebsd11.0
>> -emit-obj -mrelax-all -disable-free -main-file-name
>> minmax_init_list_comp.pass.cpp -mrelocation-model static -mthread-model
>> posix -mdisable-fp-elim -masm-verbose -mconstructor-aliases -munwind-tables
>> -target-cpu x86-64 -v -v -dwarf-column-info -debugger-tuning=gdb
>> -coverage-notes-file /w/bld/org/projects/libcxx/tes
>> t/std/algorithms/alg.sorting/alg.min.max/Output/minmax_init_list_comp.pass.cpp.gcno
>> -nostdinc++ -resource-dir /w/c/org/bin/../lib/clang/4.0.0 -include
>> /w/src/llvm.org/projects/libcxx/test/support/nasty_macros.hpp -I /w/src/
>> llvm.org/projects/libcxx/include -I /w/src/llvm.org/projects/libcx
>> x/test/support -D LIBCXX_FILESYSTEM_STATIC_TEST_ROOT=/w/src/
>> llvm.org/projects/libcxx/test/std/experimental/f
>> ilesystem/Inputs/static_test_env -D LIBCXX_FILESYSTEM_DYNAMIC_TEST
>> _ROOT=/w/bld/org/projects/libcxx/test/filesystem/Output/dynamic_env -D
>> LIBCXX_FILESYSTEM_DYNAMIC_TEST_HELPER=/usr/local/bin/python2.7 /w/src/
>> llvm.org/projects/libcxx/test/support/filesystem_dynamic_test_helper.py
>> -Werror=thread-safety -std=c++1z -fdeprecated-macro -fdebug-compilation-dir
>> /w/src/llvm.org -ferror-limit 19 -fmessage-length 210
>> -fobjc-runtime=gnustep -fcxx-exceptions -fexceptions
>> -fdiagnostics-show-option -fcolor-diagnostics -o
>> /w/bld/org/projects/libcxx/test/std/algorithms/alg.sorting/a
>> lg.min.max/Output/minmax_init_list_comp.pass.cpp.o -x c++ /w/src/
>> llvm.org/projects/libcxx/test/std/algorithms/alg.sort
>> ing/alg.min.max/minmax_init_list_comp.pass.cpp
>> clang -cc1 version 4.0.0 based upon LLVM 4.0.0svn default target
>> x86_64-unknown-freebsd11.0
>> #include "..." search starts here:
>> #include <...> search starts here:
>> /w/src/llvm.org/projects/libcxx/include
>> /w/src/llvm.org/projects/libcxx/test/support
>> /w/c/org/bin/../lib/clang/4.0.0/include
>> /usr/include
>> End of search list.
>> /w/src/llvm.org/projects/libcxx/test/std/algorithms/alg.sort
>> ing/alg.min.max/minmax_init_list_comp.pass.cpp:68:19: error:
>> static_assert expression is not an integral constant expression
>> static_assert((std::minmax({1, 2, 3}, std::greater<int>()) ==
>> std::pair<int, int>(3, 1)), "");
>>
>> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> ~~~~~~~~~~~~~~
>> /w/src/llvm.org/projects/libcxx/include/algorithm:2823:12: note:
>> non-constexpr constructor 'pair' cannot be used in a constant expression
>> return __result;
>> ^
>> /w/src/llvm.org/projects/libcxx/test/std/algorithms/alg.sort
>> ing/alg.min.max/minmax_init_list_comp.pass.cpp:68:20: note: in call to
>> 'minmax({&{1, 2, 3}[0], 3}, {{}})'
>> static_assert((std::minmax({1, 2, 3}, std::greater<int>()) ==
>> std::pair<int, int>(3, 1)), "");
>> ^
>> /w/src/llvm.org/projects/libcxx/include/utility:316:5: note: declared
>> here
>> pair(pair&& __p) _NOEXCEPT_(is_nothrow_move_constructible<first_type>::value
>> &&
>> ^
>> /w/src/llvm.org/projects/libcxx/test/std/algorithms/alg.sort
>> ing/alg.min.max/minmax_init_list_comp.pass.cpp:69:19: error:
>> static_assert expression is not an integral constant expression
>> static_assert((std::minmax({1, 3, 2}, std::greater<int>()) ==
>> std::pair<int, int>(3, 1)), "");
>>
>> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> ~~~~~~~~~~~~~~
>> /w/src/llvm.org/projects/libcxx/include/algorithm:2823:12: note:
>> non-constexpr constructor 'pair' cannot be used in a constant expression
>> return __result;
>> ^
>> /w/src/llvm.org/projects/libcxx/test/std/algorithms/alg.sort
>> ing/alg.min.max/minmax_init_list_comp.pass.cpp:69:20: note: in call to
>> 'minmax({&{1, 3, 2}[0], 3}, {{}})'
>> static_assert((std::minmax({1, 3, 2}, std::greater<int>()) ==
>> std::pair<int, int>(3, 1)), "");
>> ^
>> /w/src/llvm.org/projects/libcxx/include/utility:316:5: note: declared
>> here
>> pair(pair&& __p) _NOEXCEPT_(is_nothrow_move_constructible<first_type>::value
>> &&
>> ^
>> /w/src/llvm.org/projects/libcxx/test/std/algorithms/alg.sort
>> ing/alg.min.max/minmax_init_list_comp.pass.cpp:70:19: error:
>> static_assert expression is not an integral constant expression
>> static_assert((std::minmax({2, 1, 3}, std::greater<int>()) ==
>> std::pair<int, int>(3, 1)), "");
>>
>> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> ~~~~~~~~~~~~~~
>> /w/src/llvm.org/projects/libcxx/include/algorithm:2823:12: note:
>> non-constexpr constructor 'pair' cannot be used in a constant expression
>> return __result;
>> ^
>> /w/src/llvm.org/projects/libcxx/test/std/algorithms/alg.sort
>> ing/alg.min.max/minmax_init_list_comp.pass.cpp:70:20: note: in call to
>> 'minmax({&{2, 1, 3}[0], 3}, {{}})'
>> static_assert((std::minmax({2, 1, 3}, std::greater<int>()) ==
>> std::pair<int, int>(3, 1)), "");
>> ^
>> /w/src/llvm.org/projects/libcxx/include/utility:316:5: note: declared
>> here
>> pair(pair&& __p) _NOEXCEPT_(is_nothrow_move_constructible<first_type>::value
>> &&
>> ^
>> /w/src/llvm.org/projects/libcxx/test/std/algorithms/alg.sort
>> ing/alg.min.max/minmax_init_list_comp.pass.cpp:71:19: error:
>> static_assert expression is not an integral constant expression
>> static_assert((std::minmax({2, 3, 1}, std::greater<int>()) ==
>> std::pair<int, int>(3, 1)), "");
>>
>> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> ~~~~~~~~~~~~~~
>> /w/src/llvm.org/projects/libcxx/include/algorithm:2823:12: note:
>> non-constexpr constructor 'pair' cannot be used in a constant expression
>> return __result;
>> ^
>> /w/src/llvm.org/projects/libcxx/test/std/algorithms/alg.sort
>> ing/alg.min.max/minmax_init_list_comp.pass.cpp:71:20: note: in call to
>> 'minmax({&{2, 3, 1}[0], 3}, {{}})'
>> static_assert((std::minmax({2, 3, 1}, std::greater<int>()) ==
>> std::pair<int, int>(3, 1)), "");
>> ^
>> /w/src/llvm.org/projects/libcxx/include/utility:316:5: note: declared
>> here
>> pair(pair&& __p) _NOEXCEPT_(is_nothrow_move_constructible<first_type>::value
>> &&
>> ^
>> /w/src/llvm.org/projects/libcxx/test/std/algorithms/alg.sort
>> ing/alg.min.max/minmax_init_list_comp.pass.cpp:72:19: error:
>> static_assert expression is not an integral constant expression
>> static_assert((std::minmax({3, 1, 2}, std::greater<int>()) ==
>> std::pair<int, int>(3, 1)), "");
>>
>> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> ~~~~~~~~~~~~~~
>> /w/src/llvm.org/projects/libcxx/include/algorithm:2823:12: note:
>> non-constexpr constructor 'pair' cannot be used in a constant expression
>> return __result;
>> ^
>> /w/src/llvm.org/projects/libcxx/test/std/algorithms/alg.sort
>> ing/alg.min.max/minmax_init_list_comp.pass.cpp:72:20: note: in call to
>> 'minmax({&{3, 1, 2}[0], 3}, {{}})'
>> static_assert((std::minmax({3, 1, 2}, std::greater<int>()) ==
>> std::pair<int, int>(3, 1)), "");
>> ^
>> /w/src/llvm.org/projects/libcxx/include/utility:316:5: note: declared
>> here
>> pair(pair&& __p) _NOEXCEPT_(is_nothrow_move_constructible<first_type>::value
>> &&
>> ^
>> /w/src/llvm.org/projects/libcxx/test/std/algorithms/alg.sort
>> ing/alg.min.max/minmax_init_list_comp.pass.cpp:73:19: error:
>> static_assert expression is not an integral constant expression
>> static_assert((std::minmax({3, 2, 1}, std::greater<int>()) ==
>> std::pair<int, int>(3, 1)), "");
>>
>> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> ~~~~~~~~~~~~~~
>> /w/src/llvm.org/projects/libcxx/include/algorithm:2823:12: note:
>> non-constexpr constructor 'pair' cannot be used in a constant expression
>> return __result;
>> ^
>> /w/src/llvm.org/projects/libcxx/test/std/algorithms/alg.sort
>> ing/alg.min.max/minmax_init_list_comp.pass.cpp:73:20: note: in call to
>> 'minmax({&{3, 2, 1}[0], 3}, {{}})'
>> static_assert((std::minmax({3, 2, 1}, std::greater<int>()) ==
>> std::pair<int, int>(3, 1)), "");
>> ^
>> /w/src/llvm.org/projects/libcxx/include/utility:316:5: note: declared
>> here
>> pair(pair&& __p) _NOEXCEPT_(is_nothrow_move_constructible<first_type>::value
>> &&
>> ^
>> 6 errors generated.
>>
>>
>> -Krzysztof
>>
>> _______________________________________________
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>
>
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