[cfe-dev] Unexpected check-libcxx failures on FreeBSD
Eric Fiselier via cfe-dev
cfe-dev at lists.llvm.org
Fri Oct 7 19:31:21 PDT 2016
In my infinite cleverness I think I found a solution which gives both
constexpr and non-trivial constructors.
Please take a look at https://reviews.llvm.org/D25389.
/Eric
On Fri, Oct 7, 2016 at 8:11 PM, Eric Fiselier <eric at efcs.ca> wrote:
> 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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