https://github.com/llvmbot created https://github.com/llvm/llvm-project/pull/138674
Backport 25fc52e655fb4bfd3bb89948d5cbfe011e1b8984 Requested by: @ldionne >From be87564873d74080a5a45bb79221690c3fd4b740 Mon Sep 17 00:00:00 2001 From: Louis Dionne <ldionn...@gmail.com> Date: Mon, 5 May 2025 17:19:13 -0400 Subject: [PATCH] [libc++] Re-introduce _LIBCPP_DISABLE_AVAILABILITY (#134158) The `_LIBCPP_DISABLE_AVAILABILITY` macro was removed in afae1a5f32bb as an intended no-op. It turns out that some projects are making use of that macro to work around a Clang bug with availability annotations that still exists: https://github.com/llvm/llvm-project/issues/134151. Since that Clang bug still hasn't been fixed, I feel that we must sill honor that unfortunate macro until we've figured out how to get rid of it without breaking code. (cherry picked from commit 25fc52e655fb4bfd3bb89948d5cbfe011e1b8984) --- libcxx/docs/ReleaseNotes/20.rst | 3 -- libcxx/include/__configuration/availability.h | 8 ++- .../vendor/apple/disable-availability.sh.cpp | 49 +++++++++++++++++++ 3 files changed, 56 insertions(+), 4 deletions(-) create mode 100644 libcxx/test/libcxx/vendor/apple/disable-availability.sh.cpp diff --git a/libcxx/docs/ReleaseNotes/20.rst b/libcxx/docs/ReleaseNotes/20.rst index 06e6e673b5508..f81a573845e6f 100644 --- a/libcxx/docs/ReleaseNotes/20.rst +++ b/libcxx/docs/ReleaseNotes/20.rst @@ -153,9 +153,6 @@ Deprecations and Removals headers as an extension and only deprecates them. The ``_LIBCPP_DISABLE_DEPRECATION_WARNINGS`` macro can be defined to suppress deprecation for these headers. -- The ``_LIBCPP_DISABLE_AVAILABILITY`` macro that was used to force-disable availability markup has now been removed. - Whether availability markup is used by the library is now solely controlled at configuration-time. - - The pointer safety functions ``declare_reachable``, ``declare_no_pointers``, ``undeclare_no_pointers`` and ``__undeclare_reachable`` have been removed from the library. These functions were never implemented in a non-trivial way, making it very unlikely that any binary depends on them. diff --git a/libcxx/include/__configuration/availability.h b/libcxx/include/__configuration/availability.h index f9e52a690c05c..aa2e75b6f6fe8 100644 --- a/libcxx/include/__configuration/availability.h +++ b/libcxx/include/__configuration/availability.h @@ -69,7 +69,13 @@ // Availability markup is disabled when building the library, or when a non-Clang // compiler is used because only Clang supports the necessary attributes. -#if defined(_LIBCPP_BUILDING_LIBRARY) || defined(_LIBCXXABI_BUILDING_LIBRARY) || !defined(_LIBCPP_COMPILER_CLANG_BASED) +// +// We also allow users to force-disable availability markup via the `_LIBCPP_DISABLE_AVAILABILITY` +// macro because that is the only way to work around a Clang bug related to availability +// attributes: https://github.com/llvm/llvm-project/issues/134151. +// Once that bug has been fixed, we should remove the macro. +#if defined(_LIBCPP_BUILDING_LIBRARY) || defined(_LIBCXXABI_BUILDING_LIBRARY) || \ + !defined(_LIBCPP_COMPILER_CLANG_BASED) || defined(_LIBCPP_DISABLE_AVAILABILITY) # undef _LIBCPP_HAS_VENDOR_AVAILABILITY_ANNOTATIONS # define _LIBCPP_HAS_VENDOR_AVAILABILITY_ANNOTATIONS 0 #endif diff --git a/libcxx/test/libcxx/vendor/apple/disable-availability.sh.cpp b/libcxx/test/libcxx/vendor/apple/disable-availability.sh.cpp new file mode 100644 index 0000000000000..474b3f83c6044 --- /dev/null +++ b/libcxx/test/libcxx/vendor/apple/disable-availability.sh.cpp @@ -0,0 +1,49 @@ +//===----------------------------------------------------------------------===// +// +// 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 +// +//===----------------------------------------------------------------------===// + +// REQUIRES: stdlib=apple-libc++ + +// This test is dependent on the code generated by the compiler, and it doesn't +// work properly with older AppleClangs. +// UNSUPPORTED: apple-clang-15 + +// This test ensures that we retain a way to disable availability markup on Apple platforms +// in order to work around Clang bug https://github.com/llvm/llvm-project/issues/134151. +// +// Once that bug has been fixed or once we've made changes to libc++'s use of availability +// that render that workaround unnecessary, the macro and this test can be removed. +// +// The test works by creating a final linked image that refers to a function marked with +// both an availability attribute and with _LIBCPP_HIDE_FROM_ABI. We then check that this +// generates a weak reference to the function -- without the bug, we'd expect a strong +// reference or no reference at all instead. + +// First, test the test. Make sure that we do (incorrectly) produce a weak definition when we +// don't define _LIBCPP_DISABLE_AVAILABILITY. Otherwise, something may have changed in libc++ +// and this test might not work anymore. +// RUN: %{cxx} %s %{flags} %{compile_flags} %{link_flags} -fvisibility=hidden -fvisibility-inlines-hidden -shared -o %t.1.dylib +// RUN: nm -m %t.1.dylib | c++filt | grep value > %t.1.symbols +// RUN: grep weak %t.1.symbols + +// Now, make sure that 'weak' goes away when we define _LIBCPP_DISABLE_AVAILABILITY. +// In fact, all references to the function might go away, so we just check that we don't emit +// any weak reference. +// RUN: %{cxx} %s %{flags} %{compile_flags} %{link_flags} -fvisibility=hidden -fvisibility-inlines-hidden -D_LIBCPP_DISABLE_AVAILABILITY -shared -o %t.2.dylib +// RUN: nm -m %t.2.dylib | c++filt | grep value > %t.2.symbols +// RUN: not grep weak %t.2.symbols + +#include <version> + +template <class T> +struct optional { + T val_; + _LIBCPP_HIDE_FROM_ABI _LIBCPP_INTRODUCED_IN_LLVM_11_ATTRIBUTE T value() const { return val_; } +}; + +using PMF = int (optional<int>::*)() const; +PMF f() { return &optional<int>::value; } _______________________________________________ llvm-branch-commits mailing list llvm-branch-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
