https://github.com/ldionne updated https://github.com/llvm/llvm-project/pull/69498
>From 77c0256c3ae99808a8def68bfcf5eee2fad704ca Mon Sep 17 00:00:00 2001 From: Louis Dionne <ldionn...@gmail.com> Date: Wed, 14 Jun 2023 17:49:22 -0700 Subject: [PATCH 1/8] [libc++] Fix the behavior of throwing `operator new` under -fno-exceptions In D144319, Clang tried to land a change that would cause some functions that are not supposed to return nullptr to optimize better. As reported in https://reviews.llvm.org/D144319#4203982, libc++ started seeing failures in its CI shortly after this change was landed. As explained in D146379, the reason for these failures is that libc++'s throwing `operator new` can in fact return nullptr when compiled with exceptions disabled. However, this contradicts the Standard, which clearly says that the throwing version of `operator new(size_t)` should never return nullptr. This is actually a long standing issue. I've previously seen a case where LTO would optimize incorrectly based on the assumption that `operator new` doesn't return nullptr, an assumption that was violated in that case because libc++.dylib was compiled with -fno-exceptions. Unfortunately, fixing this is kind of tricky. The Standard has a few requirements for the allocation functions, some of which are impossible to satisfy under -fno-exceptions: 1. `operator new(size_t)` must never return nullptr 2. `operator new(size_t, nothrow_t)` must call the throwing version and return nullptr on failure to allocate 3. We can't throw exceptions when compiled with -fno-exceptions In the case where exceptions are enabled, things work nicely. `new(size_t)` throws and `new(size_t, nothrow_t)` uses a try-catch to return nullptr. However, when compiling the library with -fno-exceptions, we can't throw an exception from `new(size_t)`, and we can't catch anything from `new(size_t, nothrow_t)`. The only thing we can do from `new(size_t)` is actually abort the program, which does not make it possible for `new(size_t, nothrow_t)` to catch something and return nullptr. This patch makes the following changes: 1. When compiled with -fno-exceptions, the throwing version of `operator new` will now abort on failure instead of returning nullptr on failure. This resolves the issue that the compiler could mis-compile based on the assumption that nullptr is never returned. This constitutes an API and ABI breaking change for folks compiling the library with -fno-exceptions (which is not the general public, who merely uses libc++ headers but use a shared library that has already been compiled). This should mostly impact vendors and other folks who compile libc++.dylib themselves. 2. When the library is compiled with -fexceptions, the nothrow version of `operator new` has no change. When the library is compiled with -fno-exceptions, the nothrow version of `operator new` will now check whether the throwing version of `operator new` has been overridden. If it has not been overridden, then it will use an implementation equivalent to that of the throwing `operator new`, except it will return nullptr on failure to allocate (instead of terminating). However, if the throwing `operator new` has been overridden, it is now an error NOT to also override the nothrow `operator new`. Indeed, there is no way for us to implement a valid nothrow `operator new` without knowing the exact implementation of the throwing version. rdar://103958777 Differential Revision: https://reviews.llvm.org/D150610 --- libcxx/docs/ReleaseNotes/18.rst | 23 +++++ libcxx/include/CMakeLists.txt | 1 + libcxx/include/__overridable_function | 38 ++++++++ libcxx/include/new | 9 +- libcxx/src/new.cpp | 79 +++++++++++----- ...new_not_overridden_fno_exceptions.pass.cpp | 56 ++++++++++++ .../new_dont_return_nullptr.pass.cpp | 37 ++++++++ libcxx/test/support/check_assertion.h | 6 ++ libcxxabi/src/stdlib_new_delete.cpp | 90 ++++++++++++++----- 9 files changed, 291 insertions(+), 48 deletions(-) create mode 100644 libcxx/include/__overridable_function create mode 100644 libcxx/test/libcxx/language.support/support.dynamic/assert.nothrow_new_not_overridden_fno_exceptions.pass.cpp create mode 100644 libcxx/test/libcxx/language.support/support.dynamic/new_dont_return_nullptr.pass.cpp diff --git a/libcxx/docs/ReleaseNotes/18.rst b/libcxx/docs/ReleaseNotes/18.rst index ac78563aa73848f..bf017613a01b892 100644 --- a/libcxx/docs/ReleaseNotes/18.rst +++ b/libcxx/docs/ReleaseNotes/18.rst @@ -118,6 +118,29 @@ LLVM 20 ABI Affecting Changes --------------------- +- When the shared/static library is built with ``-fno-exceptions``, the behavior of ``operator new`` was changed + to make it standards-conforming. In LLVM 17 and before, the throwing versions of ``operator new`` would return + ``nullptr`` upon failure to allocate, when the shared/static library was built with exceptions disabled. This + was non-conforming, since the throwing versions of ``operator new`` are never expected to return ``nullptr``, and + this non-conformance could actually lead to miscompiles in subtle cases. + + Starting in LLVM 18, the throwing versions of ``operator new`` will abort the program when they fail to allocate + if the shared/static library has been built with ``-fno-exceptions``. This is consistent with the behavior of all + other potentially-throwing functions in the library, which abort the program instead of throwing when ``-fno-exceptions`` + is used. + + Furthermore, when the shared/static library is built with ``-fno-exceptions``, users who override the throwing + version of ``operator new`` will now need to also override the ``std::nothrow_t`` version of ``operator new`` if + they want to use it. Indeed, this is because there is no way to implement a conforming ``operator new(nothrow)`` + from a conforming potentially-throwing ``operator new`` when compiled with ``-fno-exceptions``. In that case, using + ``operator new(nothrow)`` without overriding it explicitly but after overriding the throwing ``operator new`` will + result in an error. + + Note that this change only impacts vendors/users that build the shared/static library themselves and pass + ``-DLIBCXX_ENABLE_EXCEPTIONS=OFF``, which is not the default configuration. If you are using the default + configuration of the library, the libc++ shared/static library will be built with exceptions enabled, and + there is no change between LLVM 17 and LLVM 18, even for users who build their own code using ``-fno-exceptions``. + - The symbol of a non-visible function part of ``std::system_error`` was removed. This is not a breaking change as the private function ``__init`` was never referenced internally outside of the dylib diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt index 9b03430a87d8338..064b9cd3ed8973b 100644 --- a/libcxx/include/CMakeLists.txt +++ b/libcxx/include/CMakeLists.txt @@ -565,6 +565,7 @@ set(files __numeric/transform_exclusive_scan.h __numeric/transform_inclusive_scan.h __numeric/transform_reduce.h + __overridable_function __random/bernoulli_distribution.h __random/binomial_distribution.h __random/cauchy_distribution.h diff --git a/libcxx/include/__overridable_function b/libcxx/include/__overridable_function new file mode 100644 index 000000000000000..941a731e7bc2120 --- /dev/null +++ b/libcxx/include/__overridable_function @@ -0,0 +1,38 @@ +// -*- C++ -*- +//===----------------------------------------------------------------------===// +// +// 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 _LIBCPP___OVERRIDABLE_FUNCTION +#define _LIBCPP___OVERRIDABLE_FUNCTION + +#include <__config> +#include <cstdint> + +_LIBCPP_BEGIN_NAMESPACE_STD + +#define _LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE \ + __attribute__((__section__("__TEXT,__lcxx_override,regular,pure_instructions"))) + +template <class _Ret, class... _Args> +_LIBCPP_HIDE_FROM_ABI bool __is_function_overridden(_Ret (*__ptr)(_Args...)) noexcept { + // The linker places these at the start/end of the __lcxx_override section, + // which is where we put the definitions for any overridable function, via + // _LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE. + // + // Placing the function in a separate section allows for this logic to be applied + // even in the scenario where clients are statically linking against libc++/libc++abi. + extern const uintptr_t __lcxx_override_start __asm("section$start$__TEXT$__lcxx_override"); + extern const uintptr_t __lcxx_override_end __asm("section$end$__TEXT$__lcxx_override"); + uintptr_t* __uptr = reinterpret_cast<uintptr_t*>(__ptr); + + return __uptr < &__lcxx_override_start || __uptr > &__lcxx_override_end; +} + +_LIBCPP_END_NAMESPACE_STD + +#endif // _LIBCPP___OVERRIDABLE_FUNCTION diff --git a/libcxx/include/new b/libcxx/include/new index 0a97c3e37add574..caeb9a5c8b4b811 100644 --- a/libcxx/include/new +++ b/libcxx/include/new @@ -90,6 +90,7 @@ void operator delete[](void* ptr, void*) noexcept; #include <__availability> #include <__config> #include <__exception/exception.h> +#include <__overridable_function> #include <__type_traits/alignment_of.h> #include <__type_traits/is_function.h> #include <__type_traits/is_same.h> @@ -214,7 +215,7 @@ inline constexpr destroying_delete_t destroying_delete{}; #if !defined(_LIBCPP_ABI_VCRUNTIME) -_LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS void* operator new(std::size_t __sz) _THROW_BAD_ALLOC; +_LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS _LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE void* operator new(std::size_t __sz) _THROW_BAD_ALLOC; _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS void* operator new(std::size_t __sz, const std::nothrow_t&) _NOEXCEPT _LIBCPP_NOALIAS; _LIBCPP_OVERRIDABLE_FUNC_VIS void operator delete(void* __p) _NOEXCEPT; _LIBCPP_OVERRIDABLE_FUNC_VIS void operator delete(void* __p, const std::nothrow_t&) _NOEXCEPT; @@ -222,7 +223,7 @@ _LIBCPP_OVERRIDABLE_FUNC_VIS void operator delete(void* __p, const std::nothrow _LIBCPP_OVERRIDABLE_FUNC_VIS _LIBCPP_AVAILABILITY_SIZED_NEW_DELETE void operator delete(void* __p, std::size_t __sz) _NOEXCEPT; #endif -_LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS void* operator new[](std::size_t __sz) _THROW_BAD_ALLOC; +_LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS _LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE void* operator new[](std::size_t __sz) _THROW_BAD_ALLOC; _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS void* operator new[](std::size_t __sz, const std::nothrow_t&) _NOEXCEPT _LIBCPP_NOALIAS; _LIBCPP_OVERRIDABLE_FUNC_VIS void operator delete[](void* __p) _NOEXCEPT; _LIBCPP_OVERRIDABLE_FUNC_VIS void operator delete[](void* __p, const std::nothrow_t&) _NOEXCEPT; @@ -231,7 +232,7 @@ _LIBCPP_OVERRIDABLE_FUNC_VIS _LIBCPP_AVAILABILITY_SIZED_NEW_DELETE void operato #endif #ifndef _LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION -_LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS void* operator new(std::size_t __sz, std::align_val_t) _THROW_BAD_ALLOC; +_LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS _LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE void* operator new(std::size_t __sz, std::align_val_t) _THROW_BAD_ALLOC; _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS void* operator new(std::size_t __sz, std::align_val_t, const std::nothrow_t&) _NOEXCEPT _LIBCPP_NOALIAS; _LIBCPP_OVERRIDABLE_FUNC_VIS void operator delete(void* __p, std::align_val_t) _NOEXCEPT; _LIBCPP_OVERRIDABLE_FUNC_VIS void operator delete(void* __p, std::align_val_t, const std::nothrow_t&) _NOEXCEPT; @@ -239,7 +240,7 @@ _LIBCPP_OVERRIDABLE_FUNC_VIS void operator delete(void* __p, std::align_val_t, _LIBCPP_OVERRIDABLE_FUNC_VIS _LIBCPP_AVAILABILITY_SIZED_NEW_DELETE void operator delete(void* __p, std::size_t __sz, std::align_val_t) _NOEXCEPT; #endif -_LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS void* operator new[](std::size_t __sz, std::align_val_t) _THROW_BAD_ALLOC; +_LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS _LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE void* operator new[](std::size_t __sz, std::align_val_t) _THROW_BAD_ALLOC; _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS void* operator new[](std::size_t __sz, std::align_val_t, const std::nothrow_t&) _NOEXCEPT _LIBCPP_NOALIAS; _LIBCPP_OVERRIDABLE_FUNC_VIS void operator delete[](void* __p, std::align_val_t) _NOEXCEPT; _LIBCPP_OVERRIDABLE_FUNC_VIS void operator delete[](void* __p, std::align_val_t, const std::nothrow_t&) _NOEXCEPT; diff --git a/libcxx/src/new.cpp b/libcxx/src/new.cpp index 033bba5c1fc95b6..5cbebf74300f443 100644 --- a/libcxx/src/new.cpp +++ b/libcxx/src/new.cpp @@ -7,6 +7,8 @@ //===----------------------------------------------------------------------===// #include <__memory/aligned_alloc.h> +#include <__overridable_function> +#include <cstddef> #include <cstdlib> #include <new> @@ -15,6 +17,10 @@ // The code below is copied as-is into libc++abi's libcxxabi/src/stdlib_new_delete.cpp // file. The version in this file is the canonical one. +inline void __throw_bad_alloc_shim() { std::__throw_bad_alloc(); } + +# define _LIBCPP_ASSERT_SHIM(expr, str) _LIBCPP_ASSERT(expr, str) + // ------------------ BEGIN COPY ------------------ // Implement all new and delete operators as weak definitions // in this shared library, so that they can be overridden by programs @@ -38,39 +44,53 @@ static void* operator_new_impl(std::size_t size) noexcept { _LIBCPP_WEAK void* operator new(std::size_t size) _THROW_BAD_ALLOC { void* p = operator_new_impl(size); -# ifndef _LIBCPP_HAS_NO_EXCEPTIONS if (p == nullptr) - throw std::bad_alloc(); -# endif + __throw_bad_alloc_shim(); return p; } _LIBCPP_WEAK void* operator new(size_t size, const std::nothrow_t&) noexcept { +# ifdef _LIBCPP_HAS_NO_EXCEPTIONS + _LIBCPP_ASSERT_SHIM( + !std::__is_function_overridden(static_cast<void* (*)(std::size_t)>(&operator new)), + "libc++ was configured with exceptions disabled and `operator new(size_t)` has been overridden, " + "but `operator new(size_t, nothrow_t)` has not been overridden. This is problematic because " + "`operator new(size_t, nothrow_t)` must call `operator new(size_t)`, which will terminate in case " + "it fails to allocate, making it impossible for `operator new(size_t, nothrow_t)` to fulfill its " + "contract (since it should return nullptr upon failure)."); + + return operator_new_impl(size); +# else void* p = nullptr; -# ifndef _LIBCPP_HAS_NO_EXCEPTIONS try { -# endif // _LIBCPP_HAS_NO_EXCEPTIONS p = ::operator new(size); -# ifndef _LIBCPP_HAS_NO_EXCEPTIONS } catch (...) { } -# endif // _LIBCPP_HAS_NO_EXCEPTIONS return p; +# endif } _LIBCPP_WEAK void* operator new[](size_t size) _THROW_BAD_ALLOC { return ::operator new(size); } _LIBCPP_WEAK void* operator new[](size_t size, const std::nothrow_t&) noexcept { +# ifdef _LIBCPP_HAS_NO_EXCEPTIONS + _LIBCPP_ASSERT_SHIM( + !std::__is_function_overridden(static_cast<void* (*)(std::size_t)>(&operator new[])), + "libc++ was configured with exceptions disabled and `operator new[](size_t)` has been overridden, " + "but `operator new[](size_t, nothrow_t)` has not been overridden. This is problematic because " + "`operator new[](size_t, nothrow_t)` must call `operator new[](size_t)`, which will terminate in case " + "it fails to allocate, making it impossible for `operator new[](size_t, nothrow_t)` to fulfill its " + "contract (since it should return nullptr upon failure)."); + + return operator_new_impl(size); +# else void* p = nullptr; -# ifndef _LIBCPP_HAS_NO_EXCEPTIONS try { -# endif // _LIBCPP_HAS_NO_EXCEPTIONS p = ::operator new[](size); -# ifndef _LIBCPP_HAS_NO_EXCEPTIONS } catch (...) { } -# endif // _LIBCPP_HAS_NO_EXCEPTIONS return p; +# endif } _LIBCPP_WEAK void operator delete(void* ptr) noexcept { std::free(ptr); } @@ -109,24 +129,30 @@ static void* operator_new_aligned_impl(std::size_t size, std::align_val_t alignm _LIBCPP_WEAK void* operator new(std::size_t size, std::align_val_t alignment) _THROW_BAD_ALLOC { void* p = operator_new_aligned_impl(size, alignment); -# ifndef _LIBCPP_HAS_NO_EXCEPTIONS if (p == nullptr) - throw std::bad_alloc(); -# endif + __throw_bad_alloc_shim(); return p; } _LIBCPP_WEAK void* operator new(size_t size, std::align_val_t alignment, const std::nothrow_t&) noexcept { +# ifdef _LIBCPP_HAS_NO_EXCEPTIONS + _LIBCPP_ASSERT_SHIM( + !std::__is_function_overridden(static_cast<void* (*)(std::size_t, std::align_val_t)>(&operator new)), + "libc++ was configured with exceptions disabled and `operator new(size_t, align_val_t)` has been overridden, " + "but `operator new(size_t, align_val_t, nothrow_t)` has not been overridden. This is problematic because " + "`operator new(size_t, align_val_t, nothrow_t)` must call `operator new(size_t, align_val_t)`, which will " + "terminate in case it fails to allocate, making it impossible for `operator new(size_t, align_val_t, nothrow_t)` " + "to fulfill its contract (since it should return nullptr upon failure)."); + + return operator_new_aligned_impl(size, alignment); +# else void* p = nullptr; -# ifndef _LIBCPP_HAS_NO_EXCEPTIONS try { -# endif // _LIBCPP_HAS_NO_EXCEPTIONS p = ::operator new(size, alignment); -# ifndef _LIBCPP_HAS_NO_EXCEPTIONS } catch (...) { } -# endif // _LIBCPP_HAS_NO_EXCEPTIONS return p; +# endif } _LIBCPP_WEAK void* operator new[](size_t size, std::align_val_t alignment) _THROW_BAD_ALLOC { @@ -134,16 +160,25 @@ _LIBCPP_WEAK void* operator new[](size_t size, std::align_val_t alignment) _THRO } _LIBCPP_WEAK void* operator new[](size_t size, std::align_val_t alignment, const std::nothrow_t&) noexcept { +# ifdef _LIBCPP_HAS_NO_EXCEPTIONS + _LIBCPP_ASSERT_SHIM( + !std::__is_function_overridden(static_cast<void* (*)(std::size_t, std::align_val_t)>(&operator new[])), + "libc++ was configured with exceptions disabled and `operator new[](size_t, align_val_t)` has been overridden, " + "but `operator new[](size_t, align_val_t, nothrow_t)` has not been overridden. This is problematic because " + "`operator new[](size_t, align_val_t, nothrow_t)` must call `operator new[](size_t, align_val_t)`, which will " + "terminate in case it fails to allocate, making it impossible for `operator new[](size_t, align_val_t, " + "nothrow_t)` " + "to fulfill its contract (since it should return nullptr upon failure)."); + + return operator_new_aligned_impl(size, alignment); +# else void* p = nullptr; -# ifndef _LIBCPP_HAS_NO_EXCEPTIONS try { -# endif // _LIBCPP_HAS_NO_EXCEPTIONS p = ::operator new[](size, alignment); -# ifndef _LIBCPP_HAS_NO_EXCEPTIONS } catch (...) { } -# endif // _LIBCPP_HAS_NO_EXCEPTIONS return p; +# endif } _LIBCPP_WEAK void operator delete(void* ptr, std::align_val_t) noexcept { std::__libcpp_aligned_free(ptr); } diff --git a/libcxx/test/libcxx/language.support/support.dynamic/assert.nothrow_new_not_overridden_fno_exceptions.pass.cpp b/libcxx/test/libcxx/language.support/support.dynamic/assert.nothrow_new_not_overridden_fno_exceptions.pass.cpp new file mode 100644 index 000000000000000..82c8bb90b8d8c4c --- /dev/null +++ b/libcxx/test/libcxx/language.support/support.dynamic/assert.nothrow_new_not_overridden_fno_exceptions.pass.cpp @@ -0,0 +1,56 @@ +//===----------------------------------------------------------------------===// +// +// 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 +// +//===----------------------------------------------------------------------===// + +// void* operator new(std::size_t, const std::nothrow_t&); +// void* operator new(std::size_t, std::align_val_t, const std::nothrow_t&); +// void* operator new[](std::size_t, const std::nothrow_t&); +// void* operator new[](std::size_t, std::align_val_t, const std::nothrow_t&); + +// This test ensures that we catch the case where `new` has been overridden but `new(nothrow)` +// has not been overridden, and the library is compiled with -fno-exceptions. +// +// In that case, it is impossible for libc++ to provide a Standards conforming implementation +// of `new(nothrow)`, so the only viable option is to terminate the program. + +// REQUIRES: has-unix-headers +// UNSUPPORTED: c++03 +// XFAIL: availability-verbose_abort-missing + +// TODO: We currently don't have a way to express that the built library was +// compiled with -fno-exceptions, so if the library was built with support +// for exceptions but we run the test suite without exceptions, this will +// spuriously fail. +// REQUIRES: no-exceptions + +#include <cstddef> +#include <new> + +#include "check_assertion.h" + +// Override the throwing versions of operator new, but not the nothrow versions. +alignas(32) char DummyData[32 * 3]; +void* operator new(std::size_t) { return DummyData; } +void* operator new(std::size_t, std::align_val_t) { return DummyData; } +void* operator new[](std::size_t) { return DummyData; } +void* operator new[](std::size_t, std::align_val_t) { return DummyData; } + +void operator delete(void*) noexcept {} +void operator delete(void*, std::align_val_t) noexcept {} +void operator delete[](void*) noexcept {} +void operator delete[](void*, std::align_val_t) noexcept {} + +int main(int, char**) { + std::size_t size = 3; + std::align_val_t align = static_cast<std::align_val_t>(32); + EXPECT_DEATH((void)operator new(size, std::nothrow)); + EXPECT_DEATH((void)operator new(size, align, std::nothrow)); + EXPECT_DEATH((void)operator new[](size, std::nothrow)); + EXPECT_DEATH((void)operator new[](size, align, std::nothrow)); + + return 0; +} diff --git a/libcxx/test/libcxx/language.support/support.dynamic/new_dont_return_nullptr.pass.cpp b/libcxx/test/libcxx/language.support/support.dynamic/new_dont_return_nullptr.pass.cpp new file mode 100644 index 000000000000000..93a5a12349c97e6 --- /dev/null +++ b/libcxx/test/libcxx/language.support/support.dynamic/new_dont_return_nullptr.pass.cpp @@ -0,0 +1,37 @@ +//===----------------------------------------------------------------------===// +// +// 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 +// +//===----------------------------------------------------------------------===// + +// void* operator new(std::size_t); +// void* operator new(std::size_t, std::align_val_t); +// void* operator new[](std::size_t); +// void* operator new[](std::size_t, std::align_val_t); + +// This test ensures that we abort the program instead of returning nullptr +// when we fail to satisfy the allocation request. The throwing versions of +// `operator new` must never return nullptr on failure to allocate (per the +// Standard) and the compiler actually relies on that for optimizations. +// Returning nullptr from the throwing `operator new` can basically result +// in miscompiles. + +// REQUIRES: has-unix-headers +// REQUIRES: no-exceptions +// UNSUPPORTED: c++03, c++11, c++14 + +#include <cstddef> +#include <limits> +#include <new> + +#include "check_assertion.h" + +int main(int, char**) { + EXPECT_DEATH((void)operator new(std::numeric_limits<std::size_t>::max())); + EXPECT_DEATH((void)operator new(std::numeric_limits<std::size_t>::max(), static_cast<std::align_val_t>(32))); + EXPECT_DEATH((void)operator new[](std::numeric_limits<std::size_t>::max())); + EXPECT_DEATH((void)operator new[](std::numeric_limits<std::size_t>::max(), static_cast<std::align_val_t>(32))); + return 0; +} diff --git a/libcxx/test/support/check_assertion.h b/libcxx/test/support/check_assertion.h index 98dd95b11556e6c..34e41e8f0d8eaf8 100644 --- a/libcxx/test/support/check_assertion.h +++ b/libcxx/test/support/check_assertion.h @@ -10,6 +10,7 @@ #define TEST_SUPPORT_CHECK_ASSERTION_H #include <cassert> +#include <csignal> #include <cstdarg> #include <cstddef> #include <cstdio> @@ -257,9 +258,14 @@ void std::__libcpp_verbose_abort(char const* format, ...) { std::exit(DeathTest::RK_Terminate); } +[[noreturn]] inline void abort_handler(int) { + std::exit(DeathTest::RK_Terminate); +} + template <class Func> inline bool ExpectDeath(const char* stmt, Func&& func, AssertionInfoMatcher Matcher) { std::set_terminate(terminate_handler); + std::signal(SIGABRT, abort_handler); DeathTest DT(Matcher); DeathTest::ResultKind RK = DT.Run(func); auto OnFailure = [&](const char* msg) { diff --git a/libcxxabi/src/stdlib_new_delete.cpp b/libcxxabi/src/stdlib_new_delete.cpp index 6c9990f063dde66..cfb8d78bda9d09b 100644 --- a/libcxxabi/src/stdlib_new_delete.cpp +++ b/libcxxabi/src/stdlib_new_delete.cpp @@ -7,7 +7,10 @@ //===----------------------------------------------------------------------===// #include "__cxxabi_config.h" +#include "abort_message.h" #include <__memory/aligned_alloc.h> +#include <__overridable_function> +#include <cstddef> #include <cstdlib> #include <new> @@ -25,6 +28,20 @@ # error libc++ and libc++abi seem to disagree on whether exceptions are enabled #endif +inline void __throw_bad_alloc_shim() { +#ifndef _LIBCPP_HAS_NO_EXCEPTIONS + throw std::bad_alloc(); +#else + abort_message("bad_alloc was thrown in -fno-exceptions mode"); +#endif +} + +#define _LIBCPP_ASSERT_SHIM(expr, str) \ + do { \ + if (!expr) \ + abort_message(str); \ + } while (false) + // ------------------ BEGIN COPY ------------------ // Implement all new and delete operators as weak definitions // in this shared library, so that they can be overridden by programs @@ -49,25 +66,31 @@ static void* operator_new_impl(std::size_t size) noexcept { _LIBCPP_WEAK void* operator new(std::size_t size) _THROW_BAD_ALLOC { void* p = operator_new_impl(size); -#ifndef _LIBCPP_HAS_NO_EXCEPTIONS if (p == nullptr) - throw std::bad_alloc(); -#endif + __throw_bad_alloc_shim(); return p; } _LIBCPP_WEAK void* operator new(size_t size, const std::nothrow_t&) noexcept { +#ifdef _LIBCPP_HAS_NO_EXCEPTIONS + _LIBCPP_ASSERT_SHIM( + !std::__is_function_overridden(static_cast<void* (*)(std::size_t)>(&operator new)), + "libc++ was configured with exceptions disabled and `operator new(size_t)` has been overridden, " + "but `operator new(size_t, nothrow_t)` has not been overridden. This is problematic because " + "`operator new(size_t, nothrow_t)` must call `operator new(size_t)`, which will terminate in case " + "it fails to allocate, making it impossible for `operator new(size_t, nothrow_t)` to fulfill its " + "contract (since it should return nullptr upon failure)."); + + return operator_new_impl(size); +#else void* p = nullptr; -#ifndef _LIBCPP_HAS_NO_EXCEPTIONS try { -#endif // _LIBCPP_HAS_NO_EXCEPTIONS p = ::operator new(size); -#ifndef _LIBCPP_HAS_NO_EXCEPTIONS } catch (...) { } -#endif // _LIBCPP_HAS_NO_EXCEPTIONS return p; +#endif } _LIBCPP_WEAK @@ -75,16 +98,24 @@ void* operator new[](size_t size) _THROW_BAD_ALLOC { return ::operator new(size) _LIBCPP_WEAK void* operator new[](size_t size, const std::nothrow_t&) noexcept { +#ifdef _LIBCPP_HAS_NO_EXCEPTIONS + _LIBCPP_ASSERT_SHIM( + !std::__is_function_overridden(static_cast<void* (*)(std::size_t)>(&operator new[])), + "libc++ was configured with exceptions disabled and `operator new[](size_t)` has been overridden, " + "but `operator new[](size_t, nothrow_t)` has not been overridden. This is problematic because " + "`operator new[](size_t, nothrow_t)` must call `operator new[](size_t)`, which will terminate in case " + "it fails to allocate, making it impossible for `operator new[](size_t, nothrow_t)` to fulfill its " + "contract (since it should return nullptr upon failure)."); + + return operator_new_impl(size); +#else void* p = nullptr; -#ifndef _LIBCPP_HAS_NO_EXCEPTIONS try { -#endif // _LIBCPP_HAS_NO_EXCEPTIONS p = ::operator new[](size); -#ifndef _LIBCPP_HAS_NO_EXCEPTIONS } catch (...) { } -#endif // _LIBCPP_HAS_NO_EXCEPTIONS return p; +#endif } _LIBCPP_WEAK @@ -130,25 +161,31 @@ static void* operator_new_aligned_impl(std::size_t size, std::align_val_t alignm _LIBCPP_WEAK void* operator new(std::size_t size, std::align_val_t alignment) _THROW_BAD_ALLOC { void* p = operator_new_aligned_impl(size, alignment); -# ifndef _LIBCPP_HAS_NO_EXCEPTIONS if (p == nullptr) - throw std::bad_alloc(); -# endif + __throw_bad_alloc_shim(); return p; } _LIBCPP_WEAK void* operator new(size_t size, std::align_val_t alignment, const std::nothrow_t&) noexcept { +# ifdef _LIBCPP_HAS_NO_EXCEPTIONS + _LIBCPP_ASSERT_SHIM( + !std::__is_function_overridden(static_cast<void* (*)(std::size_t, std::align_val_t)>(&operator new)), + "libc++ was configured with exceptions disabled and `operator new(size_t, align_val_t)` has been overridden, " + "but `operator new(size_t, align_val_t, nothrow_t)` has not been overridden. This is problematic because " + "`operator new(size_t, align_val_t, nothrow_t)` must call `operator new(size_t, align_val_t)`, which will " + "terminate in case it fails to allocate, making it impossible for `operator new(size_t, align_val_t, nothrow_t)` " + "to fulfill its contract (since it should return nullptr upon failure)."); + + return operator_new_aligned_impl(size, alignment); +# else void* p = nullptr; -# ifndef _LIBCPP_HAS_NO_EXCEPTIONS try { -# endif // _LIBCPP_HAS_NO_EXCEPTIONS p = ::operator new(size, alignment); -# ifndef _LIBCPP_HAS_NO_EXCEPTIONS } catch (...) { } -# endif // _LIBCPP_HAS_NO_EXCEPTIONS return p; +# endif } _LIBCPP_WEAK @@ -158,16 +195,25 @@ void* operator new[](size_t size, std::align_val_t alignment) _THROW_BAD_ALLOC { _LIBCPP_WEAK void* operator new[](size_t size, std::align_val_t alignment, const std::nothrow_t&) noexcept { +# ifdef _LIBCPP_HAS_NO_EXCEPTIONS + _LIBCPP_ASSERT_SHIM( + !std::__is_function_overridden(static_cast<void* (*)(std::size_t, std::align_val_t)>(&operator new[])), + "libc++ was configured with exceptions disabled and `operator new[](size_t, align_val_t)` has been overridden, " + "but `operator new[](size_t, align_val_t, nothrow_t)` has not been overridden. This is problematic because " + "`operator new[](size_t, align_val_t, nothrow_t)` must call `operator new[](size_t, align_val_t)`, which will " + "terminate in case it fails to allocate, making it impossible for `operator new[](size_t, align_val_t, " + "nothrow_t)` " + "to fulfill its contract (since it should return nullptr upon failure)."); + + return operator_new_aligned_impl(size, alignment); +# else void* p = nullptr; -# ifndef _LIBCPP_HAS_NO_EXCEPTIONS try { -# endif // _LIBCPP_HAS_NO_EXCEPTIONS p = ::operator new[](size, alignment); -# ifndef _LIBCPP_HAS_NO_EXCEPTIONS } catch (...) { } -# endif // _LIBCPP_HAS_NO_EXCEPTIONS return p; +# endif } _LIBCPP_WEAK >From 0bf3564567072afc0d0d3f16153b304446d0fd9f Mon Sep 17 00:00:00 2001 From: Louis Dionne <ldionn...@gmail.com> Date: Thu, 19 Oct 2023 10:39:39 -0700 Subject: [PATCH 2/8] Fix generated files issue --- libcxx/utils/generate_iwyu_mapping.py | 2 ++ 1 file changed, 2 insertions(+) diff --git a/libcxx/utils/generate_iwyu_mapping.py b/libcxx/utils/generate_iwyu_mapping.py index 343538a6cae4819..610b784a97d6b1c 100644 --- a/libcxx/utils/generate_iwyu_mapping.py +++ b/libcxx/utils/generate_iwyu_mapping.py @@ -65,6 +65,8 @@ def generate_map(include): continue elif i == "__node_handle": public = ["map", "set", "unordered_map", "unordered_set"] + elif i == '__overridable_function': + continue elif i == "__pstl_algorithm": continue elif i == "__pstl_config_site.in": >From 669f92677d47783a6856c85f1aef05ad356bb9da Mon Sep 17 00:00:00 2001 From: Louis Dionne <ldionn...@gmail.com> Date: Thu, 19 Oct 2023 10:48:41 -0700 Subject: [PATCH 3/8] Only mark functions as overridable at their definition, not at their declaration --- libcxx/include/new | 9 ++-- libcxx/src/new.cpp | 12 +++-- libcxxabi/src/stdlib_new_delete.cpp | 70 +++++++++++++---------------- 3 files changed, 42 insertions(+), 49 deletions(-) diff --git a/libcxx/include/new b/libcxx/include/new index caeb9a5c8b4b811..0a97c3e37add574 100644 --- a/libcxx/include/new +++ b/libcxx/include/new @@ -90,7 +90,6 @@ void operator delete[](void* ptr, void*) noexcept; #include <__availability> #include <__config> #include <__exception/exception.h> -#include <__overridable_function> #include <__type_traits/alignment_of.h> #include <__type_traits/is_function.h> #include <__type_traits/is_same.h> @@ -215,7 +214,7 @@ inline constexpr destroying_delete_t destroying_delete{}; #if !defined(_LIBCPP_ABI_VCRUNTIME) -_LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS _LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE void* operator new(std::size_t __sz) _THROW_BAD_ALLOC; +_LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS void* operator new(std::size_t __sz) _THROW_BAD_ALLOC; _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS void* operator new(std::size_t __sz, const std::nothrow_t&) _NOEXCEPT _LIBCPP_NOALIAS; _LIBCPP_OVERRIDABLE_FUNC_VIS void operator delete(void* __p) _NOEXCEPT; _LIBCPP_OVERRIDABLE_FUNC_VIS void operator delete(void* __p, const std::nothrow_t&) _NOEXCEPT; @@ -223,7 +222,7 @@ _LIBCPP_OVERRIDABLE_FUNC_VIS void operator delete(void* __p, const std::nothrow _LIBCPP_OVERRIDABLE_FUNC_VIS _LIBCPP_AVAILABILITY_SIZED_NEW_DELETE void operator delete(void* __p, std::size_t __sz) _NOEXCEPT; #endif -_LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS _LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE void* operator new[](std::size_t __sz) _THROW_BAD_ALLOC; +_LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS void* operator new[](std::size_t __sz) _THROW_BAD_ALLOC; _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS void* operator new[](std::size_t __sz, const std::nothrow_t&) _NOEXCEPT _LIBCPP_NOALIAS; _LIBCPP_OVERRIDABLE_FUNC_VIS void operator delete[](void* __p) _NOEXCEPT; _LIBCPP_OVERRIDABLE_FUNC_VIS void operator delete[](void* __p, const std::nothrow_t&) _NOEXCEPT; @@ -232,7 +231,7 @@ _LIBCPP_OVERRIDABLE_FUNC_VIS _LIBCPP_AVAILABILITY_SIZED_NEW_DELETE void operato #endif #ifndef _LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION -_LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS _LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE void* operator new(std::size_t __sz, std::align_val_t) _THROW_BAD_ALLOC; +_LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS void* operator new(std::size_t __sz, std::align_val_t) _THROW_BAD_ALLOC; _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS void* operator new(std::size_t __sz, std::align_val_t, const std::nothrow_t&) _NOEXCEPT _LIBCPP_NOALIAS; _LIBCPP_OVERRIDABLE_FUNC_VIS void operator delete(void* __p, std::align_val_t) _NOEXCEPT; _LIBCPP_OVERRIDABLE_FUNC_VIS void operator delete(void* __p, std::align_val_t, const std::nothrow_t&) _NOEXCEPT; @@ -240,7 +239,7 @@ _LIBCPP_OVERRIDABLE_FUNC_VIS void operator delete(void* __p, std::align_val_t, _LIBCPP_OVERRIDABLE_FUNC_VIS _LIBCPP_AVAILABILITY_SIZED_NEW_DELETE void operator delete(void* __p, std::size_t __sz, std::align_val_t) _NOEXCEPT; #endif -_LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS _LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE void* operator new[](std::size_t __sz, std::align_val_t) _THROW_BAD_ALLOC; +_LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS void* operator new[](std::size_t __sz, std::align_val_t) _THROW_BAD_ALLOC; _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS void* operator new[](std::size_t __sz, std::align_val_t, const std::nothrow_t&) _NOEXCEPT _LIBCPP_NOALIAS; _LIBCPP_OVERRIDABLE_FUNC_VIS void operator delete[](void* __p, std::align_val_t) _NOEXCEPT; _LIBCPP_OVERRIDABLE_FUNC_VIS void operator delete[](void* __p, std::align_val_t, const std::nothrow_t&) _NOEXCEPT; diff --git a/libcxx/src/new.cpp b/libcxx/src/new.cpp index 5cbebf74300f443..29d0fa4af2734c8 100644 --- a/libcxx/src/new.cpp +++ b/libcxx/src/new.cpp @@ -42,7 +42,7 @@ static void* operator_new_impl(std::size_t size) noexcept { return p; } -_LIBCPP_WEAK void* operator new(std::size_t size) _THROW_BAD_ALLOC { +_LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE _LIBCPP_WEAK void* operator new(std::size_t size) _THROW_BAD_ALLOC { void* p = operator_new_impl(size); if (p == nullptr) __throw_bad_alloc_shim(); @@ -70,7 +70,9 @@ _LIBCPP_WEAK void* operator new(size_t size, const std::nothrow_t&) noexcept { # endif } -_LIBCPP_WEAK void* operator new[](size_t size) _THROW_BAD_ALLOC { return ::operator new(size); } +_LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE _LIBCPP_WEAK void* operator new[](size_t size) _THROW_BAD_ALLOC { + return ::operator new(size); +} _LIBCPP_WEAK void* operator new[](size_t size, const std::nothrow_t&) noexcept { # ifdef _LIBCPP_HAS_NO_EXCEPTIONS @@ -127,7 +129,8 @@ static void* operator_new_aligned_impl(std::size_t size, std::align_val_t alignm return p; } -_LIBCPP_WEAK void* operator new(std::size_t size, std::align_val_t alignment) _THROW_BAD_ALLOC { +_LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE _LIBCPP_WEAK void* +operator new(std::size_t size, std::align_val_t alignment) _THROW_BAD_ALLOC { void* p = operator_new_aligned_impl(size, alignment); if (p == nullptr) __throw_bad_alloc_shim(); @@ -155,7 +158,8 @@ _LIBCPP_WEAK void* operator new(size_t size, std::align_val_t alignment, const s # endif } -_LIBCPP_WEAK void* operator new[](size_t size, std::align_val_t alignment) _THROW_BAD_ALLOC { +_LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE _LIBCPP_WEAK void* +operator new[](size_t size, std::align_val_t alignment) _THROW_BAD_ALLOC { return ::operator new(size, alignment); } diff --git a/libcxxabi/src/stdlib_new_delete.cpp b/libcxxabi/src/stdlib_new_delete.cpp index cfb8d78bda9d09b..76da02d09ce06c6 100644 --- a/libcxxabi/src/stdlib_new_delete.cpp +++ b/libcxxabi/src/stdlib_new_delete.cpp @@ -63,16 +63,14 @@ static void* operator_new_impl(std::size_t size) noexcept { return p; } -_LIBCPP_WEAK -void* operator new(std::size_t size) _THROW_BAD_ALLOC { +_LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE _LIBCPP_WEAK void* operator new(std::size_t size) _THROW_BAD_ALLOC { void* p = operator_new_impl(size); if (p == nullptr) __throw_bad_alloc_shim(); return p; } -_LIBCPP_WEAK -void* operator new(size_t size, const std::nothrow_t&) noexcept { +_LIBCPP_WEAK void* operator new(size_t size, const std::nothrow_t&) noexcept { #ifdef _LIBCPP_HAS_NO_EXCEPTIONS _LIBCPP_ASSERT_SHIM( !std::__is_function_overridden(static_cast<void* (*)(std::size_t)>(&operator new)), @@ -93,11 +91,11 @@ void* operator new(size_t size, const std::nothrow_t&) noexcept { #endif } -_LIBCPP_WEAK -void* operator new[](size_t size) _THROW_BAD_ALLOC { return ::operator new(size); } +_LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE _LIBCPP_WEAK void* operator new[](size_t size) _THROW_BAD_ALLOC { + return ::operator new(size); +} -_LIBCPP_WEAK -void* operator new[](size_t size, const std::nothrow_t&) noexcept { +_LIBCPP_WEAK void* operator new[](size_t size, const std::nothrow_t&) noexcept { #ifdef _LIBCPP_HAS_NO_EXCEPTIONS _LIBCPP_ASSERT_SHIM( !std::__is_function_overridden(static_cast<void* (*)(std::size_t)>(&operator new[])), @@ -118,23 +116,17 @@ void* operator new[](size_t size, const std::nothrow_t&) noexcept { #endif } -_LIBCPP_WEAK -void operator delete(void* ptr) noexcept { std::free(ptr); } +_LIBCPP_WEAK void operator delete(void* ptr) noexcept { std::free(ptr); } -_LIBCPP_WEAK -void operator delete(void* ptr, const std::nothrow_t&) noexcept { ::operator delete(ptr); } +_LIBCPP_WEAK void operator delete(void* ptr, const std::nothrow_t&) noexcept { ::operator delete(ptr); } -_LIBCPP_WEAK -void operator delete(void* ptr, size_t) noexcept { ::operator delete(ptr); } +_LIBCPP_WEAK void operator delete(void* ptr, size_t) noexcept { ::operator delete(ptr); } -_LIBCPP_WEAK -void operator delete[](void* ptr) noexcept { ::operator delete(ptr); } +_LIBCPP_WEAK void operator delete[](void* ptr) noexcept { ::operator delete(ptr); } -_LIBCPP_WEAK -void operator delete[](void* ptr, const std::nothrow_t&) noexcept { ::operator delete[](ptr); } +_LIBCPP_WEAK void operator delete[](void* ptr, const std::nothrow_t&) noexcept { ::operator delete[](ptr); } -_LIBCPP_WEAK -void operator delete[](void* ptr, size_t) noexcept { ::operator delete[](ptr); } +_LIBCPP_WEAK void operator delete[](void* ptr, size_t) noexcept { ::operator delete[](ptr); } #if !defined(_LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION) @@ -158,16 +150,15 @@ static void* operator_new_aligned_impl(std::size_t size, std::align_val_t alignm return p; } -_LIBCPP_WEAK -void* operator new(std::size_t size, std::align_val_t alignment) _THROW_BAD_ALLOC { +_LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE _LIBCPP_WEAK void* +operator new(std::size_t size, std::align_val_t alignment) _THROW_BAD_ALLOC { void* p = operator_new_aligned_impl(size, alignment); if (p == nullptr) __throw_bad_alloc_shim(); return p; } -_LIBCPP_WEAK -void* operator new(size_t size, std::align_val_t alignment, const std::nothrow_t&) noexcept { +_LIBCPP_WEAK void* operator new(size_t size, std::align_val_t alignment, const std::nothrow_t&) noexcept { # ifdef _LIBCPP_HAS_NO_EXCEPTIONS _LIBCPP_ASSERT_SHIM( !std::__is_function_overridden(static_cast<void* (*)(std::size_t, std::align_val_t)>(&operator new)), @@ -188,13 +179,12 @@ void* operator new(size_t size, std::align_val_t alignment, const std::nothrow_t # endif } -_LIBCPP_WEAK -void* operator new[](size_t size, std::align_val_t alignment) _THROW_BAD_ALLOC { +_LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE _LIBCPP_WEAK void* +operator new[](size_t size, std::align_val_t alignment) _THROW_BAD_ALLOC { return ::operator new(size, alignment); } -_LIBCPP_WEAK -void* operator new[](size_t size, std::align_val_t alignment, const std::nothrow_t&) noexcept { +_LIBCPP_WEAK void* operator new[](size_t size, std::align_val_t alignment, const std::nothrow_t&) noexcept { # ifdef _LIBCPP_HAS_NO_EXCEPTIONS _LIBCPP_ASSERT_SHIM( !std::__is_function_overridden(static_cast<void* (*)(std::size_t, std::align_val_t)>(&operator new[])), @@ -216,27 +206,27 @@ void* operator new[](size_t size, std::align_val_t alignment, const std::nothrow # endif } -_LIBCPP_WEAK -void operator delete(void* ptr, std::align_val_t) noexcept { std::__libcpp_aligned_free(ptr); } +_LIBCPP_WEAK void operator delete(void* ptr, std::align_val_t) noexcept { std::__libcpp_aligned_free(ptr); } -_LIBCPP_WEAK -void operator delete(void* ptr, std::align_val_t alignment, const std::nothrow_t&) noexcept { +_LIBCPP_WEAK void operator delete(void* ptr, std::align_val_t alignment, const std::nothrow_t&) noexcept { ::operator delete(ptr, alignment); } -_LIBCPP_WEAK -void operator delete(void* ptr, size_t, std::align_val_t alignment) noexcept { ::operator delete(ptr, alignment); } +_LIBCPP_WEAK void operator delete(void* ptr, size_t, std::align_val_t alignment) noexcept { + ::operator delete(ptr, alignment); +} -_LIBCPP_WEAK -void operator delete[](void* ptr, std::align_val_t alignment) noexcept { ::operator delete(ptr, alignment); } +_LIBCPP_WEAK void operator delete[](void* ptr, std::align_val_t alignment) noexcept { + ::operator delete(ptr, alignment); +} -_LIBCPP_WEAK -void operator delete[](void* ptr, std::align_val_t alignment, const std::nothrow_t&) noexcept { +_LIBCPP_WEAK void operator delete[](void* ptr, std::align_val_t alignment, const std::nothrow_t&) noexcept { ::operator delete[](ptr, alignment); } -_LIBCPP_WEAK -void operator delete[](void* ptr, size_t, std::align_val_t alignment) noexcept { ::operator delete[](ptr, alignment); } +_LIBCPP_WEAK void operator delete[](void* ptr, size_t, std::align_val_t alignment) noexcept { + ::operator delete[](ptr, alignment); +} #endif // !_LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION // ------------------ END COPY ------------------ >From 7a9f17a4c7688958fce8bfbe80dc2e85ff37952f Mon Sep 17 00:00:00 2001 From: Louis Dionne <ldionn...@gmail.com> Date: Thu, 19 Oct 2023 10:52:31 -0700 Subject: [PATCH 4/8] Format added test --- .../support.dynamic/new_dont_return_nullptr.pass.cpp | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/libcxx/test/libcxx/language.support/support.dynamic/new_dont_return_nullptr.pass.cpp b/libcxx/test/libcxx/language.support/support.dynamic/new_dont_return_nullptr.pass.cpp index 93a5a12349c97e6..548046b0ab43d28 100644 --- a/libcxx/test/libcxx/language.support/support.dynamic/new_dont_return_nullptr.pass.cpp +++ b/libcxx/test/libcxx/language.support/support.dynamic/new_dont_return_nullptr.pass.cpp @@ -29,9 +29,9 @@ #include "check_assertion.h" int main(int, char**) { - EXPECT_DEATH((void)operator new(std::numeric_limits<std::size_t>::max())); - EXPECT_DEATH((void)operator new(std::numeric_limits<std::size_t>::max(), static_cast<std::align_val_t>(32))); - EXPECT_DEATH((void)operator new[](std::numeric_limits<std::size_t>::max())); - EXPECT_DEATH((void)operator new[](std::numeric_limits<std::size_t>::max(), static_cast<std::align_val_t>(32))); - return 0; + EXPECT_DEATH((void)operator new(std::numeric_limits<std::size_t>::max())); + EXPECT_DEATH((void)operator new(std::numeric_limits<std::size_t>::max(), static_cast<std::align_val_t>(32))); + EXPECT_DEATH((void)operator new[](std::numeric_limits<std::size_t>::max())); + EXPECT_DEATH((void)operator new[](std::numeric_limits<std::size_t>::max(), static_cast<std::align_val_t>(32))); + return 0; } >From 5a2dff7528dc7eb173ceb6b37068410ed310ed1d Mon Sep 17 00:00:00 2001 From: Louis Dionne <ldionn...@gmail.com> Date: Thu, 19 Oct 2023 12:31:12 -0700 Subject: [PATCH 5/8] Fix Python string quoting for darker --- libcxx/utils/generate_iwyu_mapping.py | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/libcxx/utils/generate_iwyu_mapping.py b/libcxx/utils/generate_iwyu_mapping.py index 610b784a97d6b1c..88840eff8f6e293 100644 --- a/libcxx/utils/generate_iwyu_mapping.py +++ b/libcxx/utils/generate_iwyu_mapping.py @@ -65,7 +65,7 @@ def generate_map(include): continue elif i == "__node_handle": public = ["map", "set", "unordered_map", "unordered_set"] - elif i == '__overridable_function': + elif i == "__overridable_function": continue elif i == "__pstl_algorithm": continue >From 87d28d737ed982fb55e2046ef08506138895c308 Mon Sep 17 00:00:00 2001 From: Louis Dionne <ldionn...@gmail.com> Date: Thu, 19 Oct 2023 12:35:45 -0700 Subject: [PATCH 6/8] Add missing pragma system header --- libcxx/include/__overridable_function | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/libcxx/include/__overridable_function b/libcxx/include/__overridable_function index 941a731e7bc2120..b7b05f45013454e 100644 --- a/libcxx/include/__overridable_function +++ b/libcxx/include/__overridable_function @@ -13,6 +13,10 @@ #include <__config> #include <cstdint> +#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) +# pragma GCC system_header +#endif + _LIBCPP_BEGIN_NAMESPACE_STD #define _LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE \ >From 7d9c0766d3e437c02da1bd70df0e4aceaa639f6c Mon Sep 17 00:00:00 2001 From: Louis Dionne <ldionn...@gmail.com> Date: Sun, 5 Nov 2023 16:12:34 -0700 Subject: [PATCH 7/8] Implement mechanism for ELF and hopefully handle platforms like Windows that lack a mechanism --- libcxx/include/__overridable_function | 101 +++++++++++++++--- libcxx/src/new.cpp | 8 ++ ...new_not_overridden_fno_exceptions.pass.cpp | 3 + libcxxabi/src/stdlib_new_delete.cpp | 8 ++ 4 files changed, 108 insertions(+), 12 deletions(-) diff --git a/libcxx/include/__overridable_function b/libcxx/include/__overridable_function index b7b05f45013454e..fa6fadfa639edef 100644 --- a/libcxx/include/__overridable_function +++ b/libcxx/include/__overridable_function @@ -19,24 +19,101 @@ _LIBCPP_BEGIN_NAMESPACE_STD -#define _LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE \ - __attribute__((__section__("__TEXT,__lcxx_override,regular,pure_instructions"))) +// +// This file provides the std::__is_function_overridden utility, which allows checking +// whether an overridable function (typically a weak symbol) like `operator new` +// has been overridden by a user or not. +// +// This is a low-level utility which does not work on all platforms, since it needs +// to make assumptions about the object file format in use. Furthermore, it requires +// the "base definition" of the function (the one we want to check whether it has been +// overridden) to be annotated with the _LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE macro. +// +// This currently works with Mach-O files (used on Darwin) and with ELF files (used on Linux +// and others). On platforms where we know how to implement this detection, the macro +// _LIBCPP_CAN_DETECT_OVERRIDDEN_FUNCTION is defined to 1, and it is defined to 0 on +// other platforms. The _LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE macro is defined to +// nothing on unsupported platforms so that it can be used to decorate functions regardless +// of whether detection is actually supported. +// +// How does this work? +// ------------------- +// +// Let's say we want to check whether a weak function `f` has been overridden by the user. +// The general mechanism works by placing `f`'s definition (in the libc++ built library) +// inside a special section, which we do using the `__section__` attribute via the +// _LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE macro. +// +// Then, when comes the time to check whether the function has been overridden, we take +// the address of the function and we check whether it falls inside the special function +// we created. This can be done by finding pointers to the start and the end of the section +// (which is done differently for ELF and Mach-O), and then checking whether `f` falls +// within those bounds. If it falls within those bounds, then `f` is still inside the +// special section and so it is the version we defined in the libc++ built library, i.e. +// it was not overridden. Otherwise, it was overridden by the user because it falls +// outside of the section. +// +// Important note +// -------------- +// +// This mechanism should never be used outside of the libc++ built library. In particular, +// attempting to use this within the libc++ headers will not work at all because we don't +// want to be defining special sections inside user's executables which use our headers. +// This is provided inside libc++'s include tree solely to make it easier to share with +// libc++abi, which needs the same mechanism. +// + +#if _LIBCPP_OBJECT_FORMAT_MACHO + +# define _LIBCPP_CAN_DETECT_OVERRIDDEN_FUNCTION 1 +# define _LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE \ + __attribute__((__section__("__TEXT,__lcxx_override,regular,pure_instructions"))) template <class _Ret, class... _Args> -_LIBCPP_HIDE_FROM_ABI bool __is_function_overridden(_Ret (*__ptr)(_Args...)) noexcept { - // The linker places these at the start/end of the __lcxx_override section, - // which is where we put the definitions for any overridable function, via - // _LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE. +_LIBCPP_HIDE_FROM_ABI bool __is_function_overridden(_Ret (*__fptr)(_Args...)) noexcept { + // Declare two dummy bytes and give them these special `__asm` values. These values are + // defined by the linker, which means that referring to `&__lcxx_override_start` will + // effectively refer to the address where the section starts (and same for the end). + extern char __lcxx_override_start __asm("section$start$__TEXT$__lcxx_override"); + extern char __lcxx_override_end __asm("section$end$__TEXT$__lcxx_override"); + + // Now get a uintptr_t out of these locations, and out of the function pointer. + uintptr_t __start = reinterpret_cast<uintptr_t>(&__lcxx_override_start); + uintptr_t __end = reinterpret_cast<uintptr_t>(&__lcxx_override_end); + uintptr_t __ptr = reinterpret_cast<uintptr_t>(__fptr); + + // Finally, the function was overridden if it falls outside of the section's bounds. + return __ptr < __start || __ptr > __end; +} + +#elif _LIBCPP_OBJECT_FORMAT_ELF + +# define _LIBCPP_CAN_DETECT_OVERRIDDEN_FUNCTION 1 +# define _LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE __attribute__((__section__("__lcxx_override"))) + +template <class _Ret, class... _Args> +_LIBCPP_HIDE_FROM_ABI bool __is_function_overridden(_Ret (*__fptr)(_Args...)) noexcept { + // This is very similar to what we do for Mach-O above. The ELF linker will implicitly define + // variables with those names corresponding to the start and the end of the section. // - // Placing the function in a separate section allows for this logic to be applied - // even in the scenario where clients are statically linking against libc++/libc++abi. - extern const uintptr_t __lcxx_override_start __asm("section$start$__TEXT$__lcxx_override"); - extern const uintptr_t __lcxx_override_end __asm("section$end$__TEXT$__lcxx_override"); - uintptr_t* __uptr = reinterpret_cast<uintptr_t*>(__ptr); + // See https://stackoverflow.com/questions/16552710/how-do-you-get-the-start-and-end-addresses-of-a-custom-elf-section + extern char __start___lcxx_override; + extern char __stop___lcxx_override; - return __uptr < &__lcxx_override_start || __uptr > &__lcxx_override_end; + uintptr_t __start = reinterpret_cast<uintptr_t>(&__start___lcxx_override); + uintptr_t __end = reinterpret_cast<uintptr_t>(&__stop___lcxx_override); + uintptr_t __ptr = reinterpret_cast<uintptr_t>(__fptr); + + return __ptr < __start || __ptr > __end; } +#else + +# define _LIBCPP_CAN_DETECT_OVERRIDDEN_FUNCTION 0 +# define _LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE /* nothing */ + +#endif + _LIBCPP_END_NAMESPACE_STD #endif // _LIBCPP___OVERRIDABLE_FUNCTION diff --git a/libcxx/src/new.cpp b/libcxx/src/new.cpp index 29d0fa4af2734c8..7a3ad4136010611 100644 --- a/libcxx/src/new.cpp +++ b/libcxx/src/new.cpp @@ -51,6 +51,7 @@ _LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE _LIBCPP_WEAK void* operator new(std _LIBCPP_WEAK void* operator new(size_t size, const std::nothrow_t&) noexcept { # ifdef _LIBCPP_HAS_NO_EXCEPTIONS +# if _LIBCPP_CAN_DETECT_OVERRIDDEN_FUNCTION _LIBCPP_ASSERT_SHIM( !std::__is_function_overridden(static_cast<void* (*)(std::size_t)>(&operator new)), "libc++ was configured with exceptions disabled and `operator new(size_t)` has been overridden, " @@ -58,6 +59,7 @@ _LIBCPP_WEAK void* operator new(size_t size, const std::nothrow_t&) noexcept { "`operator new(size_t, nothrow_t)` must call `operator new(size_t)`, which will terminate in case " "it fails to allocate, making it impossible for `operator new(size_t, nothrow_t)` to fulfill its " "contract (since it should return nullptr upon failure)."); +# endif return operator_new_impl(size); # else @@ -76,6 +78,7 @@ _LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE _LIBCPP_WEAK void* operator new[](s _LIBCPP_WEAK void* operator new[](size_t size, const std::nothrow_t&) noexcept { # ifdef _LIBCPP_HAS_NO_EXCEPTIONS +# if _LIBCPP_CAN_DETECT_OVERRIDDEN_FUNCTION _LIBCPP_ASSERT_SHIM( !std::__is_function_overridden(static_cast<void* (*)(std::size_t)>(&operator new[])), "libc++ was configured with exceptions disabled and `operator new[](size_t)` has been overridden, " @@ -83,6 +86,7 @@ _LIBCPP_WEAK void* operator new[](size_t size, const std::nothrow_t&) noexcept { "`operator new[](size_t, nothrow_t)` must call `operator new[](size_t)`, which will terminate in case " "it fails to allocate, making it impossible for `operator new[](size_t, nothrow_t)` to fulfill its " "contract (since it should return nullptr upon failure)."); +# endif return operator_new_impl(size); # else @@ -139,6 +143,7 @@ operator new(std::size_t size, std::align_val_t alignment) _THROW_BAD_ALLOC { _LIBCPP_WEAK void* operator new(size_t size, std::align_val_t alignment, const std::nothrow_t&) noexcept { # ifdef _LIBCPP_HAS_NO_EXCEPTIONS +# if _LIBCPP_CAN_DETECT_OVERRIDDEN_FUNCTION _LIBCPP_ASSERT_SHIM( !std::__is_function_overridden(static_cast<void* (*)(std::size_t, std::align_val_t)>(&operator new)), "libc++ was configured with exceptions disabled and `operator new(size_t, align_val_t)` has been overridden, " @@ -146,6 +151,7 @@ _LIBCPP_WEAK void* operator new(size_t size, std::align_val_t alignment, const s "`operator new(size_t, align_val_t, nothrow_t)` must call `operator new(size_t, align_val_t)`, which will " "terminate in case it fails to allocate, making it impossible for `operator new(size_t, align_val_t, nothrow_t)` " "to fulfill its contract (since it should return nullptr upon failure)."); +# endif return operator_new_aligned_impl(size, alignment); # else @@ -165,6 +171,7 @@ operator new[](size_t size, std::align_val_t alignment) _THROW_BAD_ALLOC { _LIBCPP_WEAK void* operator new[](size_t size, std::align_val_t alignment, const std::nothrow_t&) noexcept { # ifdef _LIBCPP_HAS_NO_EXCEPTIONS +# if _LIBCPP_CAN_DETECT_OVERRIDDEN_FUNCTION _LIBCPP_ASSERT_SHIM( !std::__is_function_overridden(static_cast<void* (*)(std::size_t, std::align_val_t)>(&operator new[])), "libc++ was configured with exceptions disabled and `operator new[](size_t, align_val_t)` has been overridden, " @@ -173,6 +180,7 @@ _LIBCPP_WEAK void* operator new[](size_t size, std::align_val_t alignment, const "terminate in case it fails to allocate, making it impossible for `operator new[](size_t, align_val_t, " "nothrow_t)` " "to fulfill its contract (since it should return nullptr upon failure)."); +# endif return operator_new_aligned_impl(size, alignment); # else diff --git a/libcxx/test/libcxx/language.support/support.dynamic/assert.nothrow_new_not_overridden_fno_exceptions.pass.cpp b/libcxx/test/libcxx/language.support/support.dynamic/assert.nothrow_new_not_overridden_fno_exceptions.pass.cpp index 82c8bb90b8d8c4c..7aa51b365f74eba 100644 --- a/libcxx/test/libcxx/language.support/support.dynamic/assert.nothrow_new_not_overridden_fno_exceptions.pass.cpp +++ b/libcxx/test/libcxx/language.support/support.dynamic/assert.nothrow_new_not_overridden_fno_exceptions.pass.cpp @@ -21,6 +21,9 @@ // UNSUPPORTED: c++03 // XFAIL: availability-verbose_abort-missing +// We only know how to diagnose this on platforms that use the ELF or Mach-O object file formats. +// XFAIL: target={{.+}}-windows-{{.+}} + // TODO: We currently don't have a way to express that the built library was // compiled with -fno-exceptions, so if the library was built with support // for exceptions but we run the test suite without exceptions, this will diff --git a/libcxxabi/src/stdlib_new_delete.cpp b/libcxxabi/src/stdlib_new_delete.cpp index 76da02d09ce06c6..5bd9b5e58b36c6a 100644 --- a/libcxxabi/src/stdlib_new_delete.cpp +++ b/libcxxabi/src/stdlib_new_delete.cpp @@ -72,6 +72,7 @@ _LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE _LIBCPP_WEAK void* operator new(std _LIBCPP_WEAK void* operator new(size_t size, const std::nothrow_t&) noexcept { #ifdef _LIBCPP_HAS_NO_EXCEPTIONS +# if _LIBCPP_CAN_DETECT_OVERRIDDEN_FUNCTION _LIBCPP_ASSERT_SHIM( !std::__is_function_overridden(static_cast<void* (*)(std::size_t)>(&operator new)), "libc++ was configured with exceptions disabled and `operator new(size_t)` has been overridden, " @@ -79,6 +80,7 @@ _LIBCPP_WEAK void* operator new(size_t size, const std::nothrow_t&) noexcept { "`operator new(size_t, nothrow_t)` must call `operator new(size_t)`, which will terminate in case " "it fails to allocate, making it impossible for `operator new(size_t, nothrow_t)` to fulfill its " "contract (since it should return nullptr upon failure)."); +# endif return operator_new_impl(size); #else @@ -97,6 +99,7 @@ _LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE _LIBCPP_WEAK void* operator new[](s _LIBCPP_WEAK void* operator new[](size_t size, const std::nothrow_t&) noexcept { #ifdef _LIBCPP_HAS_NO_EXCEPTIONS +# if _LIBCPP_CAN_DETECT_OVERRIDDEN_FUNCTION _LIBCPP_ASSERT_SHIM( !std::__is_function_overridden(static_cast<void* (*)(std::size_t)>(&operator new[])), "libc++ was configured with exceptions disabled and `operator new[](size_t)` has been overridden, " @@ -104,6 +107,7 @@ _LIBCPP_WEAK void* operator new[](size_t size, const std::nothrow_t&) noexcept { "`operator new[](size_t, nothrow_t)` must call `operator new[](size_t)`, which will terminate in case " "it fails to allocate, making it impossible for `operator new[](size_t, nothrow_t)` to fulfill its " "contract (since it should return nullptr upon failure)."); +# endif return operator_new_impl(size); #else @@ -160,6 +164,7 @@ operator new(std::size_t size, std::align_val_t alignment) _THROW_BAD_ALLOC { _LIBCPP_WEAK void* operator new(size_t size, std::align_val_t alignment, const std::nothrow_t&) noexcept { # ifdef _LIBCPP_HAS_NO_EXCEPTIONS +# if _LIBCPP_CAN_DETECT_OVERRIDDEN_FUNCTION _LIBCPP_ASSERT_SHIM( !std::__is_function_overridden(static_cast<void* (*)(std::size_t, std::align_val_t)>(&operator new)), "libc++ was configured with exceptions disabled and `operator new(size_t, align_val_t)` has been overridden, " @@ -167,6 +172,7 @@ _LIBCPP_WEAK void* operator new(size_t size, std::align_val_t alignment, const s "`operator new(size_t, align_val_t, nothrow_t)` must call `operator new(size_t, align_val_t)`, which will " "terminate in case it fails to allocate, making it impossible for `operator new(size_t, align_val_t, nothrow_t)` " "to fulfill its contract (since it should return nullptr upon failure)."); +# endif return operator_new_aligned_impl(size, alignment); # else @@ -186,6 +192,7 @@ operator new[](size_t size, std::align_val_t alignment) _THROW_BAD_ALLOC { _LIBCPP_WEAK void* operator new[](size_t size, std::align_val_t alignment, const std::nothrow_t&) noexcept { # ifdef _LIBCPP_HAS_NO_EXCEPTIONS +# if _LIBCPP_CAN_DETECT_OVERRIDDEN_FUNCTION _LIBCPP_ASSERT_SHIM( !std::__is_function_overridden(static_cast<void* (*)(std::size_t, std::align_val_t)>(&operator new[])), "libc++ was configured with exceptions disabled and `operator new[](size_t, align_val_t)` has been overridden, " @@ -194,6 +201,7 @@ _LIBCPP_WEAK void* operator new[](size_t size, std::align_val_t alignment, const "terminate in case it fails to allocate, making it impossible for `operator new[](size_t, align_val_t, " "nothrow_t)` " "to fulfill its contract (since it should return nullptr upon failure)."); +# endif return operator_new_aligned_impl(size, alignment); # else >From 41a650b7875c1528c82082a0b79ed4962a461a70 Mon Sep 17 00:00:00 2001 From: Louis Dionne <ldionn...@gmail.com> Date: Mon, 6 Nov 2023 21:52:19 -1000 Subject: [PATCH 8/8] Fix -Wundef --- libcxx/include/__overridable_function | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/libcxx/include/__overridable_function b/libcxx/include/__overridable_function index fa6fadfa639edef..3b1645273ab6746 100644 --- a/libcxx/include/__overridable_function +++ b/libcxx/include/__overridable_function @@ -63,7 +63,7 @@ _LIBCPP_BEGIN_NAMESPACE_STD // libc++abi, which needs the same mechanism. // -#if _LIBCPP_OBJECT_FORMAT_MACHO +#if defined(_LIBCPP_OBJECT_FORMAT_MACHO) # define _LIBCPP_CAN_DETECT_OVERRIDDEN_FUNCTION 1 # define _LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE \ @@ -86,7 +86,7 @@ _LIBCPP_HIDE_FROM_ABI bool __is_function_overridden(_Ret (*__fptr)(_Args...)) no return __ptr < __start || __ptr > __end; } -#elif _LIBCPP_OBJECT_FORMAT_ELF +#elif defined(_LIBCPP_OBJECT_FORMAT_ELF) # define _LIBCPP_CAN_DETECT_OVERRIDDEN_FUNCTION 1 # define _LIBCPP_MAKE_OVERRIDABLE_FUNCTION_DETECTABLE __attribute__((__section__("__lcxx_override"))) _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
