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[libc++][Android] Always redirect <stdatomic.h> to <atomic> #143036

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[libc++][Android] Always redirect <stdatomic.h> to <atomic> #143036

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5 changes: 4 additions & 1 deletion libcxx/include/atomic
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Expand Up @@ -598,7 +598,10 @@ template <class T>
# define _LIBCPP_STDATOMIC_H_HAS_DEFINITELY_BEEN_INCLUDED 0
# endif

# if _LIBCPP_STD_VER < 23 && _LIBCPP_STDATOMIC_H_HAS_DEFINITELY_BEEN_INCLUDED
// The Android LLVM toolchain has historically allowed combining the <atomic>
// and <stdatomic.h> headers in dialects before C++23, so for backwards
// compatibility, preserve that ability when targeting Android.
# if _LIBCPP_STD_VER < 23 && !defined(__ANDROID__) && _LIBCPP_STDATOMIC_H_HAS_DEFINITELY_BEEN_INCLUDED
# error <atomic> is incompatible with <stdatomic.h> before C++23. Please compile with -std=c++23.
# endif

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5 changes: 4 additions & 1 deletion libcxx/include/stdatomic.h
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Expand Up @@ -126,7 +126,10 @@ using std::atomic_signal_fence // see below
# pragma GCC system_header
# endif

# if defined(__cplusplus) && _LIBCPP_STD_VER >= 23
// The Android LLVM toolchain has historically allowed combining the <atomic>
// and <stdatomic.h> headers in dialects before C++23, so for backwards
// compatibility, preserve that ability when targeting Android.
# if defined(__cplusplus) && (_LIBCPP_STD_VER >= 23 || defined(__ANDROID__))

# include <atomic>
# include <version>
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5 changes: 4 additions & 1 deletion libcxx/test/libcxx/atomics/atomics.syn/compatible_with_stdatomic.compile.pass.cpp
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Expand Up @@ -7,7 +7,10 @@
//===----------------------------------------------------------------------===//

// UNSUPPORTED: no-threads
// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20

// On Android, libc++'s <stdatomic.h> header always redirects to <atomic>, even before C++23.
// UNSUPPORTED: c++03
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why is c++03 on a separate line now?

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It probably shouldn't be on a separate line -- it looks like libc++ does support <atomic> for C++03.

Though now I'm wondering if the UNSUPPORTED directive ought to be XFAIL instead. I think the libc++ project usually prefers XFAIL when we know that a test should fail.

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I suppose UNSUPPORTED might be fine, though, because for previous language dialects, we have the incompatible_with_stdatomic.verify.cpp test already.

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I think I'd move back c++03 on the same line as the other ones. I'm neutral on XFAIL vs UNSUPPORTED -- as you mention we already have a dedicated test for the inverse behavior.

// UNSUPPORTED: (c++11 || c++14 || c++17 || c++20) && !android

// This test verifies that <stdatomic.h> redirects to <atomic>.

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3 changes: 3 additions & 0 deletions libcxx/test/libcxx/atomics/atomics.syn/incompatible_with_stdatomic.verify.cpp
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Expand Up @@ -9,6 +9,9 @@
// UNSUPPORTED: no-threads
// REQUIRES: c++03 || c++11 || c++14 || c++17 || c++20

// On Android, libc++'s <stdatomic.h> header always redirects to <atomic>, even before C++23.
// XFAIL: android

// No diagnostic gets emitted when we build with modules.
// XFAIL: clang-modules-build

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3 changes: 3 additions & 0 deletions libcxx/test/libcxx/atomics/stdatomic.h.syn/dont_hijack_header.cxx23.compile.pass.cpp
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Expand Up @@ -21,6 +21,9 @@
// doesn't work at all if we don't use the <stdatomic.h> provided by libc++ in C++23 and above.
// XFAIL: (c++11 || c++14 || c++17 || c++20) && gcc

// On Android, libc++'s <stdatomic.h> header always redirects to <atomic>, even before C++23.
// XFAIL: android

#include <atomic>
#include <stdatomic.h>
#include <type_traits>
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