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<version> header is missing __cpp_lib_type_identity and other macros #46605

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marehr opened this issue Aug 20, 2020 · 2 comments
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<version> header is missing __cpp_lib_type_identity and other macros #46605

marehr opened this issue Aug 20, 2020 · 2 comments
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@Quuxplusone
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bugzilla Issues migrated from bugzilla libc++ libc++ C++ Standard Library. Not GNU libstdc++. Not libc++abi.

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@marehr
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marehr commented Aug 20, 2020

Bugzilla Link 47261
Version 11.0
OS Linux
CC @mclow

Extended Description

Hi clang-team,

the following code doesn't compile, even thought it can compile std::type_identity and std::unwrap_reference just fine since clang 9.0.0.

#include <type_traits>

using a = std::type_identity<int>; // works fine
using b = std::unwrap_reference_t<int>; // works fine

#ifndef __cpp_lib_type_identity
#error "Not defined?"
#endif

#ifndef __cpp_lib_unwrap_ref
#error "Not defined?"
#endif

https://godbolt.org/z/6vaa6x

I thought https://eel.is/c++draft/version.syn suggests that __cpp_lib_type_identity should be defined if it was implemented.

Thank you!
@marehr
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marehr commented Aug 21, 2020

Oops, in the haste of writing this ticket, I forgot to add -stdlib=libc++ in the compiler explorer. That means unwrap_reference_t is not implemented yet, and thus it is correct that it does not define the macro.

I should have stuck to my original observed problem:

#include <type_traits>

using a = std::type_identity<int>;

#ifndef __cpp_lib_type_identity
#error "Not defined?"
#endif

https://godbolt.org/z/KdWEfK

does not compile.

@llvmbot llvmbot transferred this issue from llvm/llvm-bugzilla-archive Dec 10, 2021
@Quuxplusone Quuxplusone self-assigned this Dec 31, 2021
@Quuxplusone
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This is now https://reviews.llvm.org/D116433

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bugzilla Issues migrated from bugzilla libc++ libc++ C++ Standard Library. Not GNU libstdc++. Not libc++abi.
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