[libc++][P0202] Marked algorithms copy/copy_n/copy_if/copy_backward constexpr.

[mclow.lists]

Nice use of __libcpp_is_constant_evaluated(), but how will that play for C++03?

[zoecarver]

__libcpp_is_constant_evaluated returns false in C++03 mode but, it still won't work as a template argument. Putting #ifs around it will probably work, though.

libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp

21

It seems like these were already here. I think it would be really great if we could instead have a single test. For all these algorithms, what I would ideally like is just to change the return type to bool, add constexpr, and return true at the end. Then we can static_assert that test succeeds. If assert fails in the test, the static_assert will also fail.

Maybe we can even develop a macro to wrap these functions and run them in both constexpr mode and normally.

[ldionne]

libcxx/include/algorithm

1717

If I'm not mistaken, __libcpp_is_constant_evaluated() is always true here, because the result is always required to be a constant expression (since it's a NTTP). This is one of the many pitfalls of this function.

Instead,I think you need to branch in the main copy() function, like so:

template <class _InputIterator, class _OutputIterator>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
_OutputIterator
copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
{
    if (__libcpp_constant_evaluated()) {
        return _VSTD::__copy_naive(__unwrap_iter(__first), __unwrap_iter(__last), __unwrap_iter(__result));
    }
    else {
        return _VSTD::__copy(__unwrap_iter(__first), __unwrap_iter(__last), __unwrap_iter(__result));
    }
}

Or something along those lines, you get the point.

libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp

21

We definitely need to run the tests in both runtime and compile-time worlds, since those exercise completely different things. Not only the code paths can be different (via is_constant_evaluated), but we also need to make sure the runtime code generated by the compiler agrees with the compile-time evaluation. So, running the tests in both assert and static_assert is needed IMO.

I don't think a lot of changes are required, because assert(condition) should be valid at compile-time if condition is true. I suggest something like the following:

#define ASSERT_CONSTEXPR(...) static_assert(((__VA_ARGS__),void(),true), "")

Then, this can be called as

ASSERT_CONSTEXPR(test<input_iterator<const int*>, output_iterator<int*> >());

without having to change test<...>() at all, I think. We could even go as far as to add ASSERT_CONSTEXPR_AFTER_CXX17(...), etc.

[mpark]

Fixed the bug around the use of __libcpp_is_constant_evaluated.

[mpark]

Updated the tests to run everything under compile-time and runtime.

[mpark]

libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp

21

For now I've moved all of the cases from main into a test() function and called test(); and static_assert(test());

Alternatively, we could maybe also add macro which does something ilke:

#if TEST_STD_VER > 17
  #define TEST_RUN_BOTH_AFTER_CXX17(...) (__VA_ARGS__); static_assert((__VA_ARGS__),void(),true)
#else
  #define TEST_RUN_BOTH_AFTER_CXX17(...) (__VA_ARGS__);
#endif

with which we could do something like:

TEST_RUN_BOTH_AFTER_CXX17(test<input_iterator<const int*>, output_iterator<int*> >());
TEST_RUN_BOTH_AFTER_CXX17(test<input_iterator<const int*>, input_iterator<int*> >());
...

The simplicity of the current approach seems fitting with the simplicity of the test suite of libc++ in general, but I don't know. I also don't know what a good name for TEST_RUN_BOTH_AFTER_CXX17 would be 😕

[ldionne]

Looks good, except for the duplicated test() functions. I'd also like to have a short discussion about how to test this (and more importantly the lack of regression w.r.t. codegen). Apart from that, I think this is good to go.

libcxx/include/algorithm

1734

This LGTM. However, one thing I just thought about is that we don't really have a way of making sure that libc++ is calling the right code at runtime vs compile-time. What I mean is that with the introduction of __libcpp_is_constant_evaluated(), we're adding a new code path that is equivalent but slower. Given some programming error (such as the previous way of dispatching on __libcpp_is_constant_evaluated(), we could conceivably end up in a situation where we always fall back to the slower (but still correct) implementation, and our tests wouldn't currently catch that.

I can't think of a way to test this at the moment, however I thought I'd at least mention it because it's a new class of potential bugs we're introducing (and against which we don't have good defence).

Edit:

Since this is really a property of the code generation, perhaps one way we could test this is by having some kind of .sh.cpp test that checks the codegen of a function calling std::copy, and confirming that for the appropriate iterator types it generates a call to memcpy. This would go in test/libcxx (since it's a property of our implementation only). Thoughts?

libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp

23

You seem to have two functions called test()?

[mpark]

Renamed the duplicate test function.

[mpark]

Removed unnecessary marking of runtime code path.

[mpark]

libcxx/include/algorithm

1734

@ldionne I took a stab at a approach that I think resembles count_new.h: https://reviews.llvm.org/differential/diff/225552/

The basic idea is to have an ExecutionTracker which can collect information about
the runtime execution path taken if _LIBCPP_TESTING_EXECUTION_PATH is defined.

1. This means that we end up with some garbage in the headers like:

#ifdef _LIBCPP_TESTING_EXECUTION_PATH
    globalExecutionPathTracker.fastPathCalled();
#endif

    const size_t __n = static_cast<size_t>(__last - __first);
    if (__n > 0)
        _VSTD::memmove(__result, __first, __n * sizeof(_Up));
    return __result + __n;

but perhaps that's not so different from other conditionals.

2. From the testing side, we have to do:

#define _LIBCPP_TESTING_EXECUTION_PATH
#include "track_execution_path.h"

#include <algorithm>

but perhaps this is not so different from random_shuffle.cxx1z.pass.cpp which does:

#define _LIBCPP_ENABLE_CXX17_REMOVED_RANDOM_SHUFFLE
#define _LIBCPP_DISABLE_DEPRECATION_WARNINGS

#include <algorithm>

[mpark]

Added missing "test_macros.h" header include.

[davezarzycki]

This breaks testing on Fedora 31 (x86_64). Is there something I'm doing wrong?

FAIL: libc++ :: std/algorithms/alg.modifying.operations/alg.copy/copy_backward.pass.cpp (50801 of 59142)
******************** TEST 'libc++ :: std/algorithms/alg.modifying.operations/alg.copy/copy_backward.pass.cpp' FAILED ********************
Command: ['/usr/bin/clang++', '-o', '/tmp/_update_lc/r/projects/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/Output/copy_backward.pass.cpp.o', '-x', 'c++', '/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_backward.pass.cpp', '-c', '-v', '-ftemplate-depth=270', '-Werror=thread-safety', '-std=c++2a', '-include', '/home/dave/s/lp/libcxx/test/support/nasty_macros.h', '-nostdinc++', '-I/home/dave/s/lp/libcxx/include', '-I/tmp/_update_lc/r/projects/libcxx/include/c++build', '-D__STDC_FORMAT_MACROS', '-D__STDC_LIMIT_MACROS', '-D__STDC_CONSTANT_MACROS', '-I/home/dave/s/lp/libcxx/test/support', '-DLIBCXX_FILESYSTEM_STATIC_TEST_ROOT="/home/dave/s/lp/libcxx/test/std/input.output/filesystems/Inputs/static_test_env"', '-DLIBCXX_FILESYSTEM_DYNAMIC_TEST_ROOT="/tmp/_update_lc/r/projects/libcxx/test/filesystem/Output/dynamic_env"', '-DLIBCXX_FILESYSTEM_DYNAMIC_TEST_HELPER="/usr/bin/python /home/dave/s/lp/libcxx/test/support/filesystem_dynamic_test_helper.py"', '-D_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER', '-Wall', '-Wextra', '-Werror', '-Wuser-defined-warnings', '-Wshadow', '-Wno-unused-command-line-argument', '-Wno-attributes', '-Wno-pessimizing-move', '-Wno-c++11-extensions', '-Wno-user-defined-literals', '-Wno-noexcept-type', '-Wsign-compare', '-Wunused-variable', '-Wunused-parameter', '-Wunreachable-code', '-c']
Exit Code: 1
Standard Error:
--
clang version 9.0.0 (Fedora 9.0.0-1.fc31)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-redhat-linux/9
Found candidate GCC installation: /usr/lib/gcc/x86_64-redhat-linux/9
Selected GCC installation: /usr/bin/../lib/gcc/x86_64-redhat-linux/9
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Selected multilib: .;@m64
 "/usr/bin/clang-9" -cc1 -triple x86_64-unknown-linux-gnu -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -discard-value-names -main-file-name copy_backward.pass.cpp -mrelocation-model static -mthread-model posix -mdisable-fp-elim -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64 -dwarf-column-info -debugger-tuning=gdb -v -coverage-notes-file /tmp/_update_lc/r/projects/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/Output/copy_backward.pass.cpp.gcno -nostdinc++ -resource-dir /usr/lib64/clang/9.0.0 -include /home/dave/s/lp/libcxx/test/support/nasty_macros.h -I /home/dave/s/lp/libcxx/include -I /tmp/_update_lc/r/projects/libcxx/include/c++build -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -D __STDC_CONSTANT_MACROS -I /home/dave/s/lp/libcxx/test/support -D "LIBCXX_FILESYSTEM_STATIC_TEST_ROOT=\"/home/dave/s/lp/libcxx/test/std/input.output/filesystems/Inputs/static_test_env\"" -D "LIBCXX_FILESYSTEM_DYNAMIC_TEST_ROOT=\"/tmp/_update_lc/r/projects/libcxx/test/filesystem/Output/dynamic_env\"" -D "LIBCXX_FILESYSTEM_DYNAMIC_TEST_HELPER=\"/usr/bin/python /home/dave/s/lp/libcxx/test/support/filesystem_dynamic_test_helper.py\"" -D _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER -internal-isystem /usr/local/include -internal-isystem /usr/lib64/clang/9.0.0/include -internal-externc-isystem /include -internal-externc-isystem /usr/include -Werror=thread-safety -Wall -Wextra -Werror -Wuser-defined-warnings -Wshadow -Wno-unused-command-line-argument -Wno-attributes -Wno-pessimizing-move -Wno-c++11-extensions -Wno-user-defined-literals -Wno-noexcept-type -Wsign-compare -Wunused-variable -Wunused-parameter -Wunreachable-code -std=c++2a -fdeprecated-macro -fdebug-compilation-dir /tmp/_update_lc/r/projects/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy -ftemplate-depth 270 -ferror-limit 19 -fmessage-length 0 -fno-implicit-modules -fobjc-runtime=gcc -fcxx-exceptions -fexceptions -fdiagnostics-show-option -faddrsig -o /tmp/_update_lc/r/projects/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/Output/copy_backward.pass.cpp.o -x c++ /home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_backward.pass.cpp
clang -cc1 version 9.0.0 based upon LLVM 9.0.0 default target x86_64-unknown-linux-gnu
ignoring nonexistent directory "/include"
#include "..." search starts here:
#include <...> search starts here:
 /home/dave/s/lp/libcxx/include
 /tmp/_update_lc/r/projects/libcxx/include/c++build
 /home/dave/s/lp/libcxx/test/support
 /usr/local/include
 /usr/lib64/clang/9.0.0/include
 /usr/include
End of search list.
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_backward.pass.cpp:28:9: error: variables defined in a constexpr function must be initialized
    int ia[N];
        ^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_backward.pass.cpp:42:5: error: no matching function for call to 'test_copy_backward'
    test_copy_backward<bidirectional_iterator<const int*>, bidirectional_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_backward.pass.cpp:25:1: note: candidate template ignored: substitution failure [with InIter = bidirectional_iterator<const int *>, OutIter = bidirectional_iterator<int *>]
test_copy_backward()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_backward.pass.cpp:43:5: error: no matching function for call to 'test_copy_backward'
    test_copy_backward<bidirectional_iterator<const int*>, random_access_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_backward.pass.cpp:25:1: note: candidate template ignored: substitution failure [with InIter = bidirectional_iterator<const int *>, OutIter = random_access_iterator<int *>]
test_copy_backward()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_backward.pass.cpp:44:5: error: no matching function for call to 'test_copy_backward'
    test_copy_backward<bidirectional_iterator<const int*>, int*>();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_backward.pass.cpp:25:1: note: candidate template ignored: substitution failure [with InIter = bidirectional_iterator<const int *>, OutIter = int *]
test_copy_backward()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_backward.pass.cpp:46:5: error: no matching function for call to 'test_copy_backward'
    test_copy_backward<random_access_iterator<const int*>, bidirectional_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_backward.pass.cpp:25:1: note: candidate template ignored: substitution failure [with InIter = random_access_iterator<const int *>, OutIter = bidirectional_iterator<int *>]
test_copy_backward()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_backward.pass.cpp:47:5: error: no matching function for call to 'test_copy_backward'
    test_copy_backward<random_access_iterator<const int*>, random_access_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_backward.pass.cpp:25:1: note: candidate template ignored: substitution failure [with InIter = random_access_iterator<const int *>, OutIter = random_access_iterator<int *>]
test_copy_backward()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_backward.pass.cpp:48:5: error: no matching function for call to 'test_copy_backward'
    test_copy_backward<random_access_iterator<const int*>, int*>();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_backward.pass.cpp:25:1: note: candidate template ignored: substitution failure [with InIter = random_access_iterator<const int *>, OutIter = int *]
test_copy_backward()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_backward.pass.cpp:50:5: error: no matching function for call to 'test_copy_backward'
    test_copy_backward<const int*, bidirectional_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_backward.pass.cpp:25:1: note: candidate template ignored: substitution failure [with InIter = const int *, OutIter = bidirectional_iterator<int *>]
test_copy_backward()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_backward.pass.cpp:51:5: error: no matching function for call to 'test_copy_backward'
    test_copy_backward<const int*, random_access_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_backward.pass.cpp:25:1: note: candidate template ignored: substitution failure [with InIter = const int *, OutIter = random_access_iterator<int *>]
test_copy_backward()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_backward.pass.cpp:52:5: error: no matching function for call to 'test_copy_backward'
    test_copy_backward<const int*, int*>();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_backward.pass.cpp:25:1: note: candidate template ignored: substitution failure [with InIter = const int *, OutIter = int *]
test_copy_backward()
^
10 errors generated.
--

Compilation failed unexpectedly!
********************
Testing:  0.. 10.. 20.. 30.. 40.. 50.. 60.. 70.. 80
FAIL: libc++ :: std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp (50804 of 59142)
******************** TEST 'libc++ :: std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp' FAILED ********************
Command: ['/usr/bin/clang++', '-o', '/tmp/_update_lc/r/projects/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/Output/copy.pass.cpp.o', '-x', 'c++', '/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp', '-c', '-v', '-ftemplate-depth=270', '-Werror=thread-safety', '-std=c++2a', '-include', '/home/dave/s/lp/libcxx/test/support/nasty_macros.h', '-nostdinc++', '-I/home/dave/s/lp/libcxx/include', '-I/tmp/_update_lc/r/projects/libcxx/include/c++build', '-D__STDC_FORMAT_MACROS', '-D__STDC_LIMIT_MACROS', '-D__STDC_CONSTANT_MACROS', '-I/home/dave/s/lp/libcxx/test/support', '-DLIBCXX_FILESYSTEM_STATIC_TEST_ROOT="/home/dave/s/lp/libcxx/test/std/input.output/filesystems/Inputs/static_test_env"', '-DLIBCXX_FILESYSTEM_DYNAMIC_TEST_ROOT="/tmp/_update_lc/r/projects/libcxx/test/filesystem/Output/dynamic_env"', '-DLIBCXX_FILESYSTEM_DYNAMIC_TEST_HELPER="/usr/bin/python /home/dave/s/lp/libcxx/test/support/filesystem_dynamic_test_helper.py"', '-D_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER', '-Wall', '-Wextra', '-Werror', '-Wuser-defined-warnings', '-Wshadow', '-Wno-unused-command-line-argument', '-Wno-attributes', '-Wno-pessimizing-move', '-Wno-c++11-extensions', '-Wno-user-defined-literals', '-Wno-noexcept-type', '-Wsign-compare', '-Wunused-variable', '-Wunused-parameter', '-Wunreachable-code', '-c']
Exit Code: 1
Standard Error:
--
clang version 9.0.0 (Fedora 9.0.0-1.fc31)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-redhat-linux/9
Found candidate GCC installation: /usr/lib/gcc/x86_64-redhat-linux/9
Selected GCC installation: /usr/bin/../lib/gcc/x86_64-redhat-linux/9
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Selected multilib: .;@m64
 "/usr/bin/clang-9" -cc1 -triple x86_64-unknown-linux-gnu -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -discard-value-names -main-file-name copy.pass.cpp -mrelocation-model static -mthread-model posix -mdisable-fp-elim -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64 -dwarf-column-info -debugger-tuning=gdb -v -coverage-notes-file /tmp/_update_lc/r/projects/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/Output/copy.pass.cpp.gcno -nostdinc++ -resource-dir /usr/lib64/clang/9.0.0 -include /home/dave/s/lp/libcxx/test/support/nasty_macros.h -I /home/dave/s/lp/libcxx/include -I /tmp/_update_lc/r/projects/libcxx/include/c++build -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -D __STDC_CONSTANT_MACROS -I /home/dave/s/lp/libcxx/test/support -D "LIBCXX_FILESYSTEM_STATIC_TEST_ROOT=\"/home/dave/s/lp/libcxx/test/std/input.output/filesystems/Inputs/static_test_env\"" -D "LIBCXX_FILESYSTEM_DYNAMIC_TEST_ROOT=\"/tmp/_update_lc/r/projects/libcxx/test/filesystem/Output/dynamic_env\"" -D "LIBCXX_FILESYSTEM_DYNAMIC_TEST_HELPER=\"/usr/bin/python /home/dave/s/lp/libcxx/test/support/filesystem_dynamic_test_helper.py\"" -D _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER -internal-isystem /usr/local/include -internal-isystem /usr/lib64/clang/9.0.0/include -internal-externc-isystem /include -internal-externc-isystem /usr/include -Werror=thread-safety -Wall -Wextra -Werror -Wuser-defined-warnings -Wshadow -Wno-unused-command-line-argument -Wno-attributes -Wno-pessimizing-move -Wno-c++11-extensions -Wno-user-defined-literals -Wno-noexcept-type -Wsign-compare -Wunused-variable -Wunused-parameter -Wunreachable-code -std=c++2a -fdeprecated-macro -fdebug-compilation-dir /tmp/_update_lc/r/projects/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy -ftemplate-depth 270 -ferror-limit 19 -fmessage-length 0 -fno-implicit-modules -fobjc-runtime=gcc -fcxx-exceptions -fexceptions -fdiagnostics-show-option -faddrsig -o /tmp/_update_lc/r/projects/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/Output/copy.pass.cpp.o -x c++ /home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp
clang -cc1 version 9.0.0 based upon LLVM 9.0.0 default target x86_64-unknown-linux-gnu
ignoring nonexistent directory "/include"
#include "..." search starts here:
#include <...> search starts here:
 /home/dave/s/lp/libcxx/include
 /tmp/_update_lc/r/projects/libcxx/include/c++build
 /home/dave/s/lp/libcxx/test/support
 /usr/local/include
 /usr/lib64/clang/9.0.0/include
 /usr/include
End of search list.
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:26:9: error: variables defined in a constexpr function must be initialized
    int ia[N];
        ^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:40:5: error: no matching function for call to 'test_copy'
    test_copy<input_iterator<const int*>, output_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:23:1: note: candidate template ignored: substitution failure [with InIter = input_iterator<const int *, const int *>, OutIter = output_iterator<int *>]
test_copy()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:41:5: error: no matching function for call to 'test_copy'
    test_copy<input_iterator<const int*>, input_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:23:1: note: candidate template ignored: substitution failure [with InIter = input_iterator<const int *, const int *>, OutIter = input_iterator<int *, int *>]
test_copy()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:42:5: error: no matching function for call to 'test_copy'
    test_copy<input_iterator<const int*>, forward_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:23:1: note: candidate template ignored: substitution failure [with InIter = input_iterator<const int *, const int *>, OutIter = forward_iterator<int *>]
test_copy()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:43:5: error: no matching function for call to 'test_copy'
    test_copy<input_iterator<const int*>, bidirectional_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:23:1: note: candidate template ignored: substitution failure [with InIter = input_iterator<const int *, const int *>, OutIter = bidirectional_iterator<int *>]
test_copy()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:44:5: error: no matching function for call to 'test_copy'
    test_copy<input_iterator<const int*>, random_access_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:23:1: note: candidate template ignored: substitution failure [with InIter = input_iterator<const int *, const int *>, OutIter = random_access_iterator<int *>]
test_copy()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:45:5: error: no matching function for call to 'test_copy'
    test_copy<input_iterator<const int*>, int*>();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:23:1: note: candidate template ignored: substitution failure [with InIter = input_iterator<const int *, const int *>, OutIter = int *]
test_copy()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:47:5: error: no matching function for call to 'test_copy'
    test_copy<forward_iterator<const int*>, output_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:23:1: note: candidate template ignored: substitution failure [with InIter = forward_iterator<const int *>, OutIter = output_iterator<int *>]
test_copy()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:48:5: error: no matching function for call to 'test_copy'
    test_copy<forward_iterator<const int*>, input_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:23:1: note: candidate template ignored: substitution failure [with InIter = forward_iterator<const int *>, OutIter = input_iterator<int *, int *>]
test_copy()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:49:5: error: no matching function for call to 'test_copy'
    test_copy<forward_iterator<const int*>, forward_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:23:1: note: candidate template ignored: substitution failure [with InIter = forward_iterator<const int *>, OutIter = forward_iterator<int *>]
test_copy()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:50:5: error: no matching function for call to 'test_copy'
    test_copy<forward_iterator<const int*>, bidirectional_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:23:1: note: candidate template ignored: substitution failure [with InIter = forward_iterator<const int *>, OutIter = bidirectional_iterator<int *>]
test_copy()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:51:5: error: no matching function for call to 'test_copy'
    test_copy<forward_iterator<const int*>, random_access_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:23:1: note: candidate template ignored: substitution failure [with InIter = forward_iterator<const int *>, OutIter = random_access_iterator<int *>]
test_copy()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:52:5: error: no matching function for call to 'test_copy'
    test_copy<forward_iterator<const int*>, int*>();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:23:1: note: candidate template ignored: substitution failure [with InIter = forward_iterator<const int *>, OutIter = int *]
test_copy()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:54:5: error: no matching function for call to 'test_copy'
    test_copy<bidirectional_iterator<const int*>, output_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:23:1: note: candidate template ignored: substitution failure [with InIter = bidirectional_iterator<const int *>, OutIter = output_iterator<int *>]
test_copy()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:55:5: error: no matching function for call to 'test_copy'
    test_copy<bidirectional_iterator<const int*>, input_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:23:1: note: candidate template ignored: substitution failure [with InIter = bidirectional_iterator<const int *>, OutIter = input_iterator<int *, int *>]
test_copy()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:56:5: error: no matching function for call to 'test_copy'
    test_copy<bidirectional_iterator<const int*>, forward_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:23:1: note: candidate template ignored: substitution failure [with InIter = bidirectional_iterator<const int *>, OutIter = forward_iterator<int *>]
test_copy()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:57:5: error: no matching function for call to 'test_copy'
    test_copy<bidirectional_iterator<const int*>, bidirectional_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:23:1: note: candidate template ignored: substitution failure [with InIter = bidirectional_iterator<const int *>, OutIter = bidirectional_iterator<int *>]
test_copy()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:58:5: error: no matching function for call to 'test_copy'
    test_copy<bidirectional_iterator<const int*>, random_access_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:23:1: note: candidate template ignored: substitution failure [with InIter = bidirectional_iterator<const int *>, OutIter = random_access_iterator<int *>]
test_copy()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:59:5: error: no matching function for call to 'test_copy'
    test_copy<bidirectional_iterator<const int*>, int*>();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp:23:1: note: candidate template ignored: substitution failure [with InIter = bidirectional_iterator<const int *>, OutIter = int *]
test_copy()
^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.
--

Compilation failed unexpectedly!
********************
Testing:  0.. 10.. 20.. 30.. 40.. 50.. 60.. 70.. 80
FAIL: libc++ :: std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp (50805 of 59142)
******************** TEST 'libc++ :: std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp' FAILED ********************
Command: ['/usr/bin/clang++', '-o', '/tmp/_update_lc/r/projects/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/Output/copy_if.pass.cpp.o', '-x', 'c++', '/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp', '-c', '-v', '-ftemplate-depth=270', '-Werror=thread-safety', '-std=c++2a', '-include', '/home/dave/s/lp/libcxx/test/support/nasty_macros.h', '-nostdinc++', '-I/home/dave/s/lp/libcxx/include', '-I/tmp/_update_lc/r/projects/libcxx/include/c++build', '-D__STDC_FORMAT_MACROS', '-D__STDC_LIMIT_MACROS', '-D__STDC_CONSTANT_MACROS', '-I/home/dave/s/lp/libcxx/test/support', '-DLIBCXX_FILESYSTEM_STATIC_TEST_ROOT="/home/dave/s/lp/libcxx/test/std/input.output/filesystems/Inputs/static_test_env"', '-DLIBCXX_FILESYSTEM_DYNAMIC_TEST_ROOT="/tmp/_update_lc/r/projects/libcxx/test/filesystem/Output/dynamic_env"', '-DLIBCXX_FILESYSTEM_DYNAMIC_TEST_HELPER="/usr/bin/python /home/dave/s/lp/libcxx/test/support/filesystem_dynamic_test_helper.py"', '-D_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER', '-Wall', '-Wextra', '-Werror', '-Wuser-defined-warnings', '-Wshadow', '-Wno-unused-command-line-argument', '-Wno-attributes', '-Wno-pessimizing-move', '-Wno-c++11-extensions', '-Wno-user-defined-literals', '-Wno-noexcept-type', '-Wsign-compare', '-Wunused-variable', '-Wunused-parameter', '-Wunreachable-code', '-c']
Exit Code: 1
Standard Error:
--
clang version 9.0.0 (Fedora 9.0.0-1.fc31)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-redhat-linux/9
Found candidate GCC installation: /usr/lib/gcc/x86_64-redhat-linux/9
Selected GCC installation: /usr/bin/../lib/gcc/x86_64-redhat-linux/9
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Selected multilib: .;@m64
 "/usr/bin/clang-9" -cc1 -triple x86_64-unknown-linux-gnu -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -discard-value-names -main-file-name copy_if.pass.cpp -mrelocation-model static -mthread-model posix -mdisable-fp-elim -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64 -dwarf-column-info -debugger-tuning=gdb -v -coverage-notes-file /tmp/_update_lc/r/projects/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/Output/copy_if.pass.cpp.gcno -nostdinc++ -resource-dir /usr/lib64/clang/9.0.0 -include /home/dave/s/lp/libcxx/test/support/nasty_macros.h -I /home/dave/s/lp/libcxx/include -I /tmp/_update_lc/r/projects/libcxx/include/c++build -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -D __STDC_CONSTANT_MACROS -I /home/dave/s/lp/libcxx/test/support -D "LIBCXX_FILESYSTEM_STATIC_TEST_ROOT=\"/home/dave/s/lp/libcxx/test/std/input.output/filesystems/Inputs/static_test_env\"" -D "LIBCXX_FILESYSTEM_DYNAMIC_TEST_ROOT=\"/tmp/_update_lc/r/projects/libcxx/test/filesystem/Output/dynamic_env\"" -D "LIBCXX_FILESYSTEM_DYNAMIC_TEST_HELPER=\"/usr/bin/python /home/dave/s/lp/libcxx/test/support/filesystem_dynamic_test_helper.py\"" -D _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER -internal-isystem /usr/local/include -internal-isystem /usr/lib64/clang/9.0.0/include -internal-externc-isystem /include -internal-externc-isystem /usr/include -Werror=thread-safety -Wall -Wextra -Werror -Wuser-defined-warnings -Wshadow -Wno-unused-command-line-argument -Wno-attributes -Wno-pessimizing-move -Wno-c++11-extensions -Wno-user-defined-literals -Wno-noexcept-type -Wsign-compare -Wunused-variable -Wunused-parameter -Wunreachable-code -std=c++2a -fdeprecated-macro -fdebug-compilation-dir /tmp/_update_lc/r/projects/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy -ftemplate-depth 270 -ferror-limit 19 -fmessage-length 0 -fno-implicit-modules -fobjc-runtime=gcc -fcxx-exceptions -fexceptions -fdiagnostics-show-option -faddrsig -o /tmp/_update_lc/r/projects/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/Output/copy_if.pass.cpp.o -x c++ /home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp
clang -cc1 version 9.0.0 based upon LLVM 9.0.0 default target x86_64-unknown-linux-gnu
ignoring nonexistent directory "/include"
#include "..." search starts here:
#include <...> search starts here:
 /home/dave/s/lp/libcxx/include
 /tmp/_update_lc/r/projects/libcxx/include/c++build
 /home/dave/s/lp/libcxx/test/support
 /usr/local/include
 /usr/lib64/clang/9.0.0/include
 /usr/include
End of search list.
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:33:9: error: variables defined in a constexpr function must be initialized
    int ia[N];
        ^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:47:5: error: no matching function for call to 'test_copy_if'
    test_copy_if<input_iterator<const int*>, output_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:30:1: note: candidate template ignored: substitution failure [with InIter = input_iterator<const int *, const int *>, OutIter = output_iterator<int *>]
test_copy_if()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:48:5: error: no matching function for call to 'test_copy_if'
    test_copy_if<input_iterator<const int*>, input_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:30:1: note: candidate template ignored: substitution failure [with InIter = input_iterator<const int *, const int *>, OutIter = input_iterator<int *, int *>]
test_copy_if()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:49:5: error: no matching function for call to 'test_copy_if'
    test_copy_if<input_iterator<const int*>, forward_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:30:1: note: candidate template ignored: substitution failure [with InIter = input_iterator<const int *, const int *>, OutIter = forward_iterator<int *>]
test_copy_if()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:50:5: error: no matching function for call to 'test_copy_if'
    test_copy_if<input_iterator<const int*>, bidirectional_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:30:1: note: candidate template ignored: substitution failure [with InIter = input_iterator<const int *, const int *>, OutIter = bidirectional_iterator<int *>]
test_copy_if()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:51:5: error: no matching function for call to 'test_copy_if'
    test_copy_if<input_iterator<const int*>, random_access_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:30:1: note: candidate template ignored: substitution failure [with InIter = input_iterator<const int *, const int *>, OutIter = random_access_iterator<int *>]
test_copy_if()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:52:5: error: no matching function for call to 'test_copy_if'
    test_copy_if<input_iterator<const int*>, int*>();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:30:1: note: candidate template ignored: substitution failure [with InIter = input_iterator<const int *, const int *>, OutIter = int *]
test_copy_if()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:54:5: error: no matching function for call to 'test_copy_if'
    test_copy_if<forward_iterator<const int*>, output_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:30:1: note: candidate template ignored: substitution failure [with InIter = forward_iterator<const int *>, OutIter = output_iterator<int *>]
test_copy_if()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:55:5: error: no matching function for call to 'test_copy_if'
    test_copy_if<forward_iterator<const int*>, input_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:30:1: note: candidate template ignored: substitution failure [with InIter = forward_iterator<const int *>, OutIter = input_iterator<int *, int *>]
test_copy_if()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:56:5: error: no matching function for call to 'test_copy_if'
    test_copy_if<forward_iterator<const int*>, forward_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:30:1: note: candidate template ignored: substitution failure [with InIter = forward_iterator<const int *>, OutIter = forward_iterator<int *>]
test_copy_if()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:57:5: error: no matching function for call to 'test_copy_if'
    test_copy_if<forward_iterator<const int*>, bidirectional_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:30:1: note: candidate template ignored: substitution failure [with InIter = forward_iterator<const int *>, OutIter = bidirectional_iterator<int *>]
test_copy_if()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:58:5: error: no matching function for call to 'test_copy_if'
    test_copy_if<forward_iterator<const int*>, random_access_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:30:1: note: candidate template ignored: substitution failure [with InIter = forward_iterator<const int *>, OutIter = random_access_iterator<int *>]
test_copy_if()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:59:5: error: no matching function for call to 'test_copy_if'
    test_copy_if<forward_iterator<const int*>, int*>();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:30:1: note: candidate template ignored: substitution failure [with InIter = forward_iterator<const int *>, OutIter = int *]
test_copy_if()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:61:5: error: no matching function for call to 'test_copy_if'
    test_copy_if<bidirectional_iterator<const int*>, output_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:30:1: note: candidate template ignored: substitution failure [with InIter = bidirectional_iterator<const int *>, OutIter = output_iterator<int *>]
test_copy_if()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:62:5: error: no matching function for call to 'test_copy_if'
    test_copy_if<bidirectional_iterator<const int*>, input_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:30:1: note: candidate template ignored: substitution failure [with InIter = bidirectional_iterator<const int *>, OutIter = input_iterator<int *, int *>]
test_copy_if()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:63:5: error: no matching function for call to 'test_copy_if'
    test_copy_if<bidirectional_iterator<const int*>, forward_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:30:1: note: candidate template ignored: substitution failure [with InIter = bidirectional_iterator<const int *>, OutIter = forward_iterator<int *>]
test_copy_if()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:64:5: error: no matching function for call to 'test_copy_if'
    test_copy_if<bidirectional_iterator<const int*>, bidirectional_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:30:1: note: candidate template ignored: substitution failure [with InIter = bidirectional_iterator<const int *>, OutIter = bidirectional_iterator<int *>]
test_copy_if()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:65:5: error: no matching function for call to 'test_copy_if'
    test_copy_if<bidirectional_iterator<const int*>, random_access_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:30:1: note: candidate template ignored: substitution failure [with InIter = bidirectional_iterator<const int *>, OutIter = random_access_iterator<int *>]
test_copy_if()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:66:5: error: no matching function for call to 'test_copy_if'
    test_copy_if<bidirectional_iterator<const int*>, int*>();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp:30:1: note: candidate template ignored: substitution failure [with InIter = bidirectional_iterator<const int *>, OutIter = int *]
test_copy_if()
^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.
--

Compilation failed unexpectedly!
********************
Testing:  0.. 10.. 20.. 30.. 40.. 50.. 60.. 70.. 80
FAIL: libc++ :: std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp (50807 of 59142)
******************** TEST 'libc++ :: std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp' FAILED ********************
Command: ['/usr/bin/clang++', '-o', '/tmp/_update_lc/r/projects/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/Output/copy_n.pass.cpp.o', '-x', 'c++', '/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp', '-c', '-v', '-ftemplate-depth=270', '-Werror=thread-safety', '-std=c++2a', '-include', '/home/dave/s/lp/libcxx/test/support/nasty_macros.h', '-nostdinc++', '-I/home/dave/s/lp/libcxx/include', '-I/tmp/_update_lc/r/projects/libcxx/include/c++build', '-D__STDC_FORMAT_MACROS', '-D__STDC_LIMIT_MACROS', '-D__STDC_CONSTANT_MACROS', '-I/home/dave/s/lp/libcxx/test/support', '-DLIBCXX_FILESYSTEM_STATIC_TEST_ROOT="/home/dave/s/lp/libcxx/test/std/input.output/filesystems/Inputs/static_test_env"', '-DLIBCXX_FILESYSTEM_DYNAMIC_TEST_ROOT="/tmp/_update_lc/r/projects/libcxx/test/filesystem/Output/dynamic_env"', '-DLIBCXX_FILESYSTEM_DYNAMIC_TEST_HELPER="/usr/bin/python /home/dave/s/lp/libcxx/test/support/filesystem_dynamic_test_helper.py"', '-D_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER', '-Wall', '-Wextra', '-Werror', '-Wuser-defined-warnings', '-Wshadow', '-Wno-unused-command-line-argument', '-Wno-attributes', '-Wno-pessimizing-move', '-Wno-c++11-extensions', '-Wno-user-defined-literals', '-Wno-noexcept-type', '-Wsign-compare', '-Wunused-variable', '-Wunused-parameter', '-Wunreachable-code', '-c']
Exit Code: 1
Standard Error:
--
clang version 9.0.0 (Fedora 9.0.0-1.fc31)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-redhat-linux/9
Found candidate GCC installation: /usr/lib/gcc/x86_64-redhat-linux/9
Selected GCC installation: /usr/bin/../lib/gcc/x86_64-redhat-linux/9
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Selected multilib: .;@m64
 "/usr/bin/clang-9" -cc1 -triple x86_64-unknown-linux-gnu -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -discard-value-names -main-file-name copy_n.pass.cpp -mrelocation-model static -mthread-model posix -mdisable-fp-elim -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64 -dwarf-column-info -debugger-tuning=gdb -v -coverage-notes-file /tmp/_update_lc/r/projects/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/Output/copy_n.pass.cpp.gcno -nostdinc++ -resource-dir /usr/lib64/clang/9.0.0 -include /home/dave/s/lp/libcxx/test/support/nasty_macros.h -I /home/dave/s/lp/libcxx/include -I /tmp/_update_lc/r/projects/libcxx/include/c++build -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -D __STDC_CONSTANT_MACROS -I /home/dave/s/lp/libcxx/test/support -D "LIBCXX_FILESYSTEM_STATIC_TEST_ROOT=\"/home/dave/s/lp/libcxx/test/std/input.output/filesystems/Inputs/static_test_env\"" -D "LIBCXX_FILESYSTEM_DYNAMIC_TEST_ROOT=\"/tmp/_update_lc/r/projects/libcxx/test/filesystem/Output/dynamic_env\"" -D "LIBCXX_FILESYSTEM_DYNAMIC_TEST_HELPER=\"/usr/bin/python /home/dave/s/lp/libcxx/test/support/filesystem_dynamic_test_helper.py\"" -D _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER -internal-isystem /usr/local/include -internal-isystem /usr/lib64/clang/9.0.0/include -internal-externc-isystem /include -internal-externc-isystem /usr/include -Werror=thread-safety -Wall -Wextra -Werror -Wuser-defined-warnings -Wshadow -Wno-unused-command-line-argument -Wno-attributes -Wno-pessimizing-move -Wno-c++11-extensions -Wno-user-defined-literals -Wno-noexcept-type -Wsign-compare -Wunused-variable -Wunused-parameter -Wunreachable-code -std=c++2a -fdeprecated-macro -fdebug-compilation-dir /tmp/_update_lc/r/projects/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy -ftemplate-depth 270 -ferror-limit 19 -fmessage-length 0 -fno-implicit-modules -fobjc-runtime=gcc -fcxx-exceptions -fexceptions -fdiagnostics-show-option -faddrsig -o /tmp/_update_lc/r/projects/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/Output/copy_n.pass.cpp.o -x c++ /home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp
clang -cc1 version 9.0.0 based upon LLVM 9.0.0 default target x86_64-unknown-linux-gnu
ignoring nonexistent directory "/include"
#include "..." search starts here:
#include <...> search starts here:
 /home/dave/s/lp/libcxx/include
 /tmp/_update_lc/r/projects/libcxx/include/c++build
 /home/dave/s/lp/libcxx/test/support
 /usr/local/include
 /usr/lib64/clang/9.0.0/include
 /usr/include
End of search list.
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:29:9: error: variables defined in a constexpr function must be initialized
    int ia[N];
        ^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:43:5: error: no matching function for call to 'test_copy_n'
    test_copy_n<input_iterator<const int*>, output_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:26:1: note: candidate template ignored: substitution failure [with InIter = input_iterator<const int *, const int *>, OutIter = output_iterator<int *>]
test_copy_n()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:44:5: error: no matching function for call to 'test_copy_n'
    test_copy_n<input_iterator<const int*>, input_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:26:1: note: candidate template ignored: substitution failure [with InIter = input_iterator<const int *, const int *>, OutIter = input_iterator<int *, int *>]
test_copy_n()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:45:5: error: no matching function for call to 'test_copy_n'
    test_copy_n<input_iterator<const int*>, forward_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:26:1: note: candidate template ignored: substitution failure [with InIter = input_iterator<const int *, const int *>, OutIter = forward_iterator<int *>]
test_copy_n()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:46:5: error: no matching function for call to 'test_copy_n'
    test_copy_n<input_iterator<const int*>, bidirectional_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:26:1: note: candidate template ignored: substitution failure [with InIter = input_iterator<const int *, const int *>, OutIter = bidirectional_iterator<int *>]
test_copy_n()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:47:5: error: no matching function for call to 'test_copy_n'
    test_copy_n<input_iterator<const int*>, random_access_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:26:1: note: candidate template ignored: substitution failure [with InIter = input_iterator<const int *, const int *>, OutIter = random_access_iterator<int *>]
test_copy_n()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:48:5: error: no matching function for call to 'test_copy_n'
    test_copy_n<input_iterator<const int*>, int*>();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:26:1: note: candidate template ignored: substitution failure [with InIter = input_iterator<const int *, const int *>, OutIter = int *]
test_copy_n()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:50:5: error: no matching function for call to 'test_copy_n'
    test_copy_n<forward_iterator<const int*>, output_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:26:1: note: candidate template ignored: substitution failure [with InIter = forward_iterator<const int *>, OutIter = output_iterator<int *>]
test_copy_n()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:51:5: error: no matching function for call to 'test_copy_n'
    test_copy_n<forward_iterator<const int*>, input_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:26:1: note: candidate template ignored: substitution failure [with InIter = forward_iterator<const int *>, OutIter = input_iterator<int *, int *>]
test_copy_n()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:52:5: error: no matching function for call to 'test_copy_n'
    test_copy_n<forward_iterator<const int*>, forward_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:26:1: note: candidate template ignored: substitution failure [with InIter = forward_iterator<const int *>, OutIter = forward_iterator<int *>]
test_copy_n()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:53:5: error: no matching function for call to 'test_copy_n'
    test_copy_n<forward_iterator<const int*>, bidirectional_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:26:1: note: candidate template ignored: substitution failure [with InIter = forward_iterator<const int *>, OutIter = bidirectional_iterator<int *>]
test_copy_n()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:54:5: error: no matching function for call to 'test_copy_n'
    test_copy_n<forward_iterator<const int*>, random_access_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:26:1: note: candidate template ignored: substitution failure [with InIter = forward_iterator<const int *>, OutIter = random_access_iterator<int *>]
test_copy_n()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:55:5: error: no matching function for call to 'test_copy_n'
    test_copy_n<forward_iterator<const int*>, int*>();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:26:1: note: candidate template ignored: substitution failure [with InIter = forward_iterator<const int *>, OutIter = int *]
test_copy_n()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:57:5: error: no matching function for call to 'test_copy_n'
    test_copy_n<bidirectional_iterator<const int*>, output_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:26:1: note: candidate template ignored: substitution failure [with InIter = bidirectional_iterator<const int *>, OutIter = output_iterator<int *>]
test_copy_n()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:58:5: error: no matching function for call to 'test_copy_n'
    test_copy_n<bidirectional_iterator<const int*>, input_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:26:1: note: candidate template ignored: substitution failure [with InIter = bidirectional_iterator<const int *>, OutIter = input_iterator<int *, int *>]
test_copy_n()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:59:5: error: no matching function for call to 'test_copy_n'
    test_copy_n<bidirectional_iterator<const int*>, forward_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:26:1: note: candidate template ignored: substitution failure [with InIter = bidirectional_iterator<const int *>, OutIter = forward_iterator<int *>]
test_copy_n()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:60:5: error: no matching function for call to 'test_copy_n'
    test_copy_n<bidirectional_iterator<const int*>, bidirectional_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:26:1: note: candidate template ignored: substitution failure [with InIter = bidirectional_iterator<const int *>, OutIter = bidirectional_iterator<int *>]
test_copy_n()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:61:5: error: no matching function for call to 'test_copy_n'
    test_copy_n<bidirectional_iterator<const int*>, random_access_iterator<int*> >();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:26:1: note: candidate template ignored: substitution failure [with InIter = bidirectional_iterator<const int *>, OutIter = random_access_iterator<int *>]
test_copy_n()
^
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:62:5: error: no matching function for call to 'test_copy_n'
    test_copy_n<bidirectional_iterator<const int*>, int*>();
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/dave/s/lp/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp:26:1: note: candidate template ignored: substitution failure [with InIter = bidirectional_iterator<const int *>, OutIter = int *]
test_copy_n()
^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.
--

Compilation failed unexpectedly!
********************

[yroux]

Same failures on ARM bots, logs are available here: http://lab.llvm.org:8011/builders/libcxx-libcxxabi-libunwind-armv7-linux/builds/1132

[ldionne]

Folks, we're aware of the CI failures, and we're working on fixing them. It's taking a bit longer than usual since we're at a committee meeting right now.

[davezarzycki]

Would you object if I revert this? Bots/CI are fairly pointless if fixes/reverts aren't timely.

[ldionne]

https://reviews.llvm.org/D69940 should fix the problems.

[davezarzycki]

In D68837#1736868, @ldionne wrote:

https://reviews.llvm.org/D69940 should fix the problems.

Thanks. Verified.

libcxx/include/algorithm

template <class ForwardIterator, class Size, class T>
     search_n(ForwardIterator first, ForwardIterator last, Size count, const T& value);
 
 template <class ForwardIterator, class Size, class T, class BinaryPredicate>
     constexpr ForwardIterator       // constexpr in C++20
     search_n(ForwardIterator first, ForwardIterator last,
              Size count, const T& value, BinaryPredicate pred);
 
 template <class InputIterator, class OutputIterator>
-    OutputIterator
+    constexpr OutputIterator      // constexpr in C++20
     copy(InputIterator first, InputIterator last, OutputIterator result);
 
 template<class InputIterator, class OutputIterator, class Predicate>
-    OutputIterator
+    constexpr OutputIterator      // constexpr in C++20
     copy_if(InputIterator first, InputIterator last,
             OutputIterator result, Predicate pred);
 
 template<class InputIterator, class Size, class OutputIterator>
-    OutputIterator
+    constexpr OutputIterator      // constexpr in C++20
     copy_n(InputIterator first, Size n, OutputIterator result);
 
 template <class BidirectionalIterator1, class BidirectionalIterator2>
-    BidirectionalIterator2
+    constexpr BidirectionalIterator2      // constexpr in C++20
     copy_backward(BidirectionalIterator1 first, BidirectionalIterator1 last,
                   BidirectionalIterator2 result);
 
 template <class ForwardIterator1, class ForwardIterator2>
     ForwardIterator2
     swap_ranges(ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2);
 
 template <class ForwardIterator1, class ForwardIterator2>

 {
     typedef typename iterator_traits<_ForwardIterator>::value_type __v;
     return _VSTD::search_n(__first, __last, __convert_to_integral(__count),
                            __value_, __equal_to<__v, _Tp>());
 }
 
 // copy
 template <class _Iter>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 _Iter
 __unwrap_iter(_Iter __i)
 {
     return __i;
 }
 
 template <class _Tp>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 typename enable_if
 <
     is_trivially_copy_assignable<_Tp>::value,
     _Tp*
 >::type
 __unwrap_iter(move_iterator<_Tp*> __i)
 {
     return __i.base();

 __unwrap_iter(__wrap_iter<_Tp*> __i)
 {
     return __i;
 }
 
 #endif  // _LIBCPP_DEBUG_LEVEL < 2
 
 template <class _InputIterator, class _OutputIterator>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 _OutputIterator
-__copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
+__copy_constexpr(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
 {
     for (; __first != __last; ++__first, (void) ++__result)
         *__result = *__first;
     return __result;
 }
 
+template <class _InputIterator, class _OutputIterator>
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
+_OutputIterator
+__copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
+{
+    return __copy_constexpr(__first, __last, __result);
+}
+
 template <class _Tp, class _Up>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 typename enable_if
 <
     is_same<typename remove_const<_Tp>::type, _Up>::value &&
     is_trivially_copy_assignable<_Up>::value,
     _Up*
 >::type
 __copy(_Tp* __first, _Tp* __last, _Up* __result)
 {
     const size_t __n = static_cast<size_t>(__last - __first);
     if (__n > 0)
         _VSTD::memmove(__result, __first, __n * sizeof(_Up));
     return __result + __n;
 }
 
 template <class _InputIterator, class _OutputIterator>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 _OutputIterator
 copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
 {
-    return _VSTD::__copy(__unwrap_iter(__first), __unwrap_iter(__last), __unwrap_iter(__result));
+  if (__libcpp_is_constant_evaluated()) {
+    return _VSTD::__copy_constexpr(
+        __unwrap_iter(__first), __unwrap_iter(__last), __unwrap_iter(__result));
+  } else {
+    return _VSTD::__copy(
+        __unwrap_iter(__first), __unwrap_iter(__last), __unwrap_iter(__result));
+  }
 }
 
 // copy_backward
 
 template <class _BidirectionalIterator, class _OutputIterator>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 _OutputIterator
-__copy_backward(_BidirectionalIterator __first, _BidirectionalIterator __last, _OutputIterator __result)
+__copy_backward_constexpr(_BidirectionalIterator __first, _BidirectionalIterator __last,
+                          _OutputIterator __result)
 {
     while (__first != __last)
         *--__result = *--__last;
     return __result;
 }
 
+template <class _BidirectionalIterator, class _OutputIterator>
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
+_OutputIterator
+__copy_backward(_BidirectionalIterator __first, _BidirectionalIterator __last,
+                _OutputIterator __result)
+{
+    return __copy_backward_constexpr(__first, __last, __result);
+}
+
 template <class _Tp, class _Up>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 typename enable_if
 <
     is_same<typename remove_const<_Tp>::type, _Up>::value &&
     is_trivially_copy_assignable<_Up>::value,
     _Up*
 >::type
 __copy_backward(_Tp* __first, _Tp* __last, _Up* __result)
 {
     const size_t __n = static_cast<size_t>(__last - __first);
     if (__n > 0)
     {
         __result -= __n;
         _VSTD::memmove(__result, __first, __n * sizeof(_Up));
     }
     return __result;
 }
 
 template <class _BidirectionalIterator1, class _BidirectionalIterator2>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 _BidirectionalIterator2
 copy_backward(_BidirectionalIterator1 __first, _BidirectionalIterator1 __last,
               _BidirectionalIterator2 __result)
 {
+    if (__libcpp_is_constant_evaluated()) {
+      return _VSTD::__copy_backward_constexpr(__unwrap_iter(__first),
+                                              __unwrap_iter(__last),
+                                              __unwrap_iter(__result));
+    } else {
       return _VSTD::__copy_backward(__unwrap_iter(__first),
                                     __unwrap_iter(__last),
                                     __unwrap_iter(__result));
     }
+}
 
 // copy_if
 
 template<class _InputIterator, class _OutputIterator, class _Predicate>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 _OutputIterator
 copy_if(_InputIterator __first, _InputIterator __last,
         _OutputIterator __result, _Predicate __pred)
 {
     for (; __first != __last; ++__first)
     {
         if (__pred(*__first))
         {
             *__result = *__first;
             ++__result;
         }
     }
     return __result;
 }
 
 // copy_n
 
 template<class _InputIterator, class _Size, class _OutputIterator>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 typename enable_if
 <
     __is_input_iterator<_InputIterator>::value &&
    !__is_random_access_iterator<_InputIterator>::value,
     _OutputIterator
 >::type
 copy_n(_InputIterator __first, _Size __orig_n, _OutputIterator __result)
 {
if (__n > 0)
             *__result = *__first;
             ++__result;
         }
     }
     return __result;
 }
 
 template<class _InputIterator, class _Size, class _OutputIterator>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 typename enable_if
 <
     __is_random_access_iterator<_InputIterator>::value,
     _OutputIterator
 >::type
 copy_n(_InputIterator __first, _Size __orig_n, _OutputIterator __result)
 {
     typedef decltype(__convert_to_integral(__orig_n)) _IntegralSize;

libcxx/include/iterator

 operator-(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT;
 #endif
 
 template <class _Iter>
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_IF_NODEBUG
 __wrap_iter<_Iter>
 operator+(typename __wrap_iter<_Iter>::difference_type, __wrap_iter<_Iter>) _NOEXCEPT;
 
-template <class _Ip, class _Op> _Op _LIBCPP_INLINE_VISIBILITY copy(_Ip, _Ip, _Op);
-template <class _B1, class _B2> _B2 _LIBCPP_INLINE_VISIBILITY copy_backward(_B1, _B1, _B2);
+template <class _Ip, class _Op> _Op _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 copy(_Ip, _Ip, _Op);
+template <class _B1, class _B2> _B2 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 copy_backward(_B1, _B1, _B2);
 template <class _Ip, class _Op> _Op _LIBCPP_INLINE_VISIBILITY move(_Ip, _Ip, _Op);
 template <class _B1, class _B2> _B2 _LIBCPP_INLINE_VISIBILITY move_backward(_B1, _B1, _B2);
 
 #if _LIBCPP_DEBUG_LEVEL < 2
 
 template <class _Tp>
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_IF_NODEBUG
 typename enable_if
#else
     operator-(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT;
 #endif
 
     template <class _Iter1>
     _LIBCPP_CONSTEXPR_IF_NODEBUG friend
     __wrap_iter<_Iter1>
     operator+(typename __wrap_iter<_Iter1>::difference_type, __wrap_iter<_Iter1>) _NOEXCEPT;
 
-    template <class _Ip, class _Op> friend _Op copy(_Ip, _Ip, _Op);
-    template <class _B1, class _B2> friend _B2 copy_backward(_B1, _B1, _B2);
+    template <class _Ip, class _Op> friend _LIBCPP_CONSTEXPR_AFTER_CXX17 _Op copy(_Ip, _Ip, _Op);
+    template <class _B1, class _B2> friend _LIBCPP_CONSTEXPR_AFTER_CXX17 _B2 copy_backward(_B1, _B1, _B2);
     template <class _Ip, class _Op> friend _Op move(_Ip, _Ip, _Op);
     template <class _B1, class _B2> friend _B2 move_backward(_B1, _B1, _B2);
 
 #if _LIBCPP_DEBUG_LEVEL < 2
     template <class _Tp>
     _LIBCPP_CONSTEXPR_IF_NODEBUG friend
     typename enable_if
     <

libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp

 //   copy(InIter first, InIter last, OutIter result);
 
 #include <algorithm>
 #include <cassert>
 
 #include "test_macros.h"
 #include "test_iterators.h"
 
-// #if TEST_STD_VER > 17
-// TEST_CONSTEXPR bool test_constexpr() {
-//     int ia[] = {1, 2, 3, 4, 5};
-//     int ic[] = {6, 6, 6, 6, 6, 6, 6};
-//
-//     auto p = std::copy(std::begin(ia), std::end(ia), std::begin(ic));
-//     return std::equal(std::begin(ia), std::end(ia), std::begin(ic), p)
-//         && std::all_of(p, std::end(ic), [](int a){return a == 6;})
-//         ;
-//     }
-// #endif
-
 template <class InIter, class OutIter>
-void
+TEST_CONSTEXPR_CXX20 void
 test()
 {
     const unsigned N = 1000;
     int ia[N];
     for (unsigned i = 0; i < N; ++i)
         ia[i] = i;
     int ib[N] = {0};
 
     OutIter r = std::copy(InIter(ia), InIter(ia+N), OutIter(ib));
     assert(base(r) == ib+N);
     for (unsigned i = 0; i < N; ++i)
         assert(ia[i] == ib[i]);
 }
 
-int main(int, char**)
+TEST_CONSTEXPR_CXX20 bool
+test()
 {
     test<input_iterator<const int*>, output_iterator<int*> >();
     test<input_iterator<const int*>, input_iterator<int*> >();
     test<input_iterator<const int*>, forward_iterator<int*> >();
     test<input_iterator<const int*>, bidirectional_iterator<int*> >();
     test<input_iterator<const int*>, random_access_iterator<int*> >();
     test<input_iterator<const int*>, int*>();
 
test()
 
     test<const int*, output_iterator<int*> >();
     test<const int*, input_iterator<int*> >();
     test<const int*, forward_iterator<int*> >();
     test<const int*, bidirectional_iterator<int*> >();
     test<const int*, random_access_iterator<int*> >();
     test<const int*, int*>();
 
-// #if TEST_STD_VER > 17
-//     static_assert(test_constexpr());
-// #endif
+  return true;
+}
+
+int main(int, char**)
+{
+    test();
+
+#if TEST_STD_VER > 17
+    static_assert(test());
+#endif
 
   return 0;
 }

libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_backward.pass.cpp

 
 #include <algorithm>
 #include <cassert>
 
 #include "test_macros.h"
 #include "test_iterators.h"
 #include "user_defined_integral.h"
 
-// #if TEST_STD_VER > 17
-// TEST_CONSTEXPR bool test_constexpr() {
-//     int ia[] = {1, 2, 3, 4, 5};
-//     int ic[] = {6, 6, 6, 6, 6, 6, 6};
-//
-//     size_t N = std::size(ia);
-//     auto p = std::copy_backward(std::begin(ia), std::end(ia), std::begin(ic) + N);
-//     return std::equal(std::begin(ic), p, std::begin(ia))
-//         && std::all_of(p, std::end(ic), [](int a){return a == 6;})
-//         ;
-//     }
-// #endif
-
 template <class InIter, class OutIter>
-void
+TEST_CONSTEXPR_CXX20 void
 test()
 {
     const unsigned N = 1000;
     int ia[N];
     for (unsigned i = 0; i < N; ++i)
         ia[i] = i;
     int ib[N] = {0};
 
     OutIter r = std::copy_backward(InIter(ia), InIter(ia+N), OutIter(ib+N));
     assert(base(r) == ib);
     for (unsigned i = 0; i < N; ++i)
         assert(ia[i] == ib[i]);
 }
 
-int main(int, char**)
+TEST_CONSTEXPR_CXX20 bool
+test()
 {
     test<bidirectional_iterator<const int*>, bidirectional_iterator<int*> >();
     test<bidirectional_iterator<const int*>, random_access_iterator<int*> >();
     test<bidirectional_iterator<const int*>, int*>();
 
     test<random_access_iterator<const int*>, bidirectional_iterator<int*> >();
     test<random_access_iterator<const int*>, random_access_iterator<int*> >();
     test<random_access_iterator<const int*>, int*>();
 
     test<const int*, bidirectional_iterator<int*> >();
     test<const int*, random_access_iterator<int*> >();
     test<const int*, int*>();
 
-// #if TEST_STD_VER > 17
-//     static_assert(test_constexpr());
-// #endif
+    return true;
+}
+
+int main(int, char**)
+{
+    test();
+
+#if TEST_STD_VER > 17
+    static_assert(test());
+#endif
 
   return 0;
 }

libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp

 //   copy_if(InIter first, InIter last, OutIter result, Pred pred);
 
 #include <algorithm>
 #include <cassert>
 
 #include "test_macros.h"
 #include "test_iterators.h"
 
-// #if TEST_STD_VER > 17
-// TEST_CONSTEXPR bool test_constexpr() {
-//     int ia[] = {2, 4, 6, 8, 6};
-//     int ic[] = {0, 0, 0, 0, 0, 0};
-//
-//     auto p = std::copy_if(std::begin(ia), std::end(ia), std::begin(ic), is6);
-//     return std::all_of(std::begin(ic), p, [](int a){return a == 6;})
-//         && std::all_of(p, std::end(ic),   [](int a){return a == 0;})
-//         ;
-//     }
-// #endif
-
 struct Pred
 {
-    bool operator()(int i) {return i % 3 == 0;}
+    TEST_CONSTEXPR_CXX14 bool operator()(int i) {return i % 3 == 0;}
 };
 
 template <class InIter, class OutIter>
-void
+TEST_CONSTEXPR_CXX20 void
 test()
 {
     const unsigned N = 1000;
     int ia[N];
     for (unsigned i = 0; i < N; ++i)
         ia[i] = i;
     int ib[N] = {0};
 
     OutIter r = std::copy_if(InIter(ia), InIter(ia+N), OutIter(ib), Pred());
     assert(base(r) == ib+N/3+1);
     for (unsigned i = 0; i < N/3+1; ++i)
         assert(ib[i] % 3 == 0);
 }
 
-int main(int, char**)
+TEST_CONSTEXPR_CXX20 bool
+test()
 {
     test<input_iterator<const int*>, output_iterator<int*> >();
     test<input_iterator<const int*>, input_iterator<int*> >();
     test<input_iterator<const int*>, forward_iterator<int*> >();
     test<input_iterator<const int*>, bidirectional_iterator<int*> >();
     test<input_iterator<const int*>, random_access_iterator<int*> >();
     test<input_iterator<const int*>, int*>();
 
test()
 
     test<const int*, output_iterator<int*> >();
     test<const int*, input_iterator<int*> >();
     test<const int*, forward_iterator<int*> >();
     test<const int*, bidirectional_iterator<int*> >();
     test<const int*, random_access_iterator<int*> >();
     test<const int*, int*>();
 
-// #if TEST_STD_VER > 17
-//     static_assert(test_constexpr());
-// #endif
+  return true;
+}
+
+int main(int, char**)
+{
+    test();
+
+#if TEST_STD_VER > 17
+    static_assert(test());
+#endif
 
   return 0;
 }

libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp

 
 #include <algorithm>
 #include <cassert>
 
 #include "test_macros.h"
 #include "test_iterators.h"
 #include "user_defined_integral.h"
 
-// #if TEST_STD_VER > 17
-// TEST_CONSTEXPR bool test_constexpr() {
-//     int ia[] = {1, 2, 3, 4, 5};
-//     int ic[] = {6, 6, 6, 6, 6, 6, 6};
-//
-//     auto p = std::copy_n(std::begin(ia), 4, std::begin(ic));
-//     return std::equal(std::begin(ic), p, std::begin(ia))
-//         && std::all_of(p, std::end(ic), [](int a){return a == 6;})
-//         ;
-//     }
-// #endif
-
 typedef UserDefinedIntegral<unsigned> UDI;
 
 template <class InIter, class OutIter>
-void
+TEST_CONSTEXPR_CXX20 void
 test()
 {
     const unsigned N = 1000;
     int ia[N];
     for (unsigned i = 0; i < N; ++i)
         ia[i] = i;
     int ib[N] = {0};
 
     OutIter r = std::copy_n(InIter(ia), UDI(N/2), OutIter(ib));
     assert(base(r) == ib+N/2);
     for (unsigned i = 0; i < N/2; ++i)
         assert(ia[i] == ib[i]);
 }
 
-int main(int, char**)
+TEST_CONSTEXPR_CXX20 bool
+test()
 {
     test<input_iterator<const int*>, output_iterator<int*> >();
     test<input_iterator<const int*>, input_iterator<int*> >();
     test<input_iterator<const int*>, forward_iterator<int*> >();
     test<input_iterator<const int*>, bidirectional_iterator<int*> >();
     test<input_iterator<const int*>, random_access_iterator<int*> >();
     test<input_iterator<const int*>, int*>();
 
test()
 
     test<const int*, output_iterator<int*> >();
     test<const int*, input_iterator<int*> >();
     test<const int*, forward_iterator<int*> >();
     test<const int*, bidirectional_iterator<int*> >();
     test<const int*, random_access_iterator<int*> >();
     test<const int*, int*>();
 
-// #if TEST_STD_VER > 17
-//     static_assert(test_constexpr());
-// #endif
+  return true;
+}
+
+int main(int, char**)
+{
+    test();
+
+#if TEST_STD_VER > 17
+    static_assert(test());
+#endif
 
   return 0;
 }

libcxx/test/support/test_iterators.h

class output_iterator
     template <class U> friend class output_iterator;
 public:
     typedef          std::output_iterator_tag                  iterator_category;
     typedef void                                               value_type;
     typedef typename std::iterator_traits<It>::difference_type difference_type;
     typedef It                                                 pointer;
     typedef typename std::iterator_traits<It>::reference       reference;
 
-    It base() const {return it_;}
+    TEST_CONSTEXPR_CXX14 It base() const {return it_;}
 
-    output_iterator () {}
-    explicit output_iterator(It it) : it_(it) {}
+    TEST_CONSTEXPR_CXX14 output_iterator () {}
+    explicit TEST_CONSTEXPR_CXX14 output_iterator(It it) : it_(it) {}
     template <class U>
-        output_iterator(const output_iterator<U>& u) :it_(u.it_) {}
+        TEST_CONSTEXPR_CXX14 output_iterator(const output_iterator<U>& u) :it_(u.it_) {}
 
-    reference operator*() const {return *it_;}
+    TEST_CONSTEXPR_CXX14 reference operator*() const {return *it_;}
 
-    output_iterator& operator++() {++it_; return *this;}
-    output_iterator operator++(int)
+    TEST_CONSTEXPR_CXX14 output_iterator& operator++() {++it_; return *this;}
+    TEST_CONSTEXPR_CXX14 output_iterator operator++(int)
         {output_iterator tmp(*this); ++(*this); return tmp;}
 
     template <class T>
     void operator,(T const &) DELETE_FUNCTION;
 };
 
 template <class It,
     class ItTraits = It>

libcxx/test/support/test_macros.h

 # else
 #   define TEST_CONSTEXPR_CXX14
 # endif
 # if TEST_STD_VER > 14
 #   define TEST_THROW_SPEC(...)
 # else
 #   define TEST_THROW_SPEC(...) throw(__VA_ARGS__)
 # endif
+# if TEST_STD_VER > 17
+#   define TEST_CONSTEXPR_CXX20 constexpr
+# else
+#   define TEST_CONSTEXPR_CXX20
+# endif
 #else
 #if defined(TEST_COMPILER_CLANG)
 # define TEST_ALIGNOF(...) _Alignof(__VA_ARGS__)
 #else
 # define TEST_ALIGNOF(...) __alignof(__VA_ARGS__)
 #endif
 #define TEST_ALIGNAS(...) __attribute__((__aligned__(__VA_ARGS__)))
 #define TEST_CONSTEXPR
 #define TEST_CONSTEXPR_CXX14
+#define TEST_CONSTEXPR_CXX20
 #define TEST_NOEXCEPT throw()
 #define TEST_NOEXCEPT_FALSE
 #define TEST_NOEXCEPT_COND(...)
 #define TEST_THROW_SPEC(...) throw(__VA_ARGS__)
 #endif
 
 // Sniff out to see if the underling C library has C11 features
 // Note that at this time (July 2018), MacOS X and iOS do NOT.

libcxx/test/support/user_defined_integral.h

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 #ifndef SUPPORT_USER_DEFINED_INTEGRAL_H
 #define SUPPORT_USER_DEFINED_INTEGRAL_H
 
 template <class T>
 struct UserDefinedIntegral
 {
-    UserDefinedIntegral() : value(0) {}
-    UserDefinedIntegral(T v) : value(v) {}
-    operator T() const { return value; }
+    TEST_CONSTEXPR_CXX14 UserDefinedIntegral() : value(0) {}
+    TEST_CONSTEXPR_CXX14 UserDefinedIntegral(T v) : value(v) {}
+    TEST_CONSTEXPR_CXX14 operator T() const { return value; }
     T value;
 };
 
 // Poison the arithmetic and comparison operations
 template <class T, class U>
 void operator+(UserDefinedIntegral<T>, UserDefinedIntegral<U>);
 
 template <class T, class U>