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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at */
#include <ostream>
#include <istream>
#include <sstream>
#include <memory>
#include <string>
#include <stdarg.h>
#include <stdio.h>
#include <mozilla/Assertions.h>
#include <cxxabi.h>
GLIBCXX_3.4.19 is from gcc 4.8.1 (199309)
GLIBCXX_3.4.20 is from gcc 4.9.0 (199307)
GLIBCXX_3.4.21 is from gcc 5.0 (210290)
GLIBCXX_3.4.22 is from gcc 6.0 (222482)
GLIBCXX_3.4.23 is from gcc 7
GLIBCXX_3.4.24 is from gcc 8
GLIBCXX_3.4.25 is from gcc 8
GLIBCXX_3.4.26 is from gcc 9
GLIBCXX_3.4.27 is from gcc 10
GLIBCXX_3.4.28 is from gcc 10
GLIBCXX_3.4.29 is from gcc 11
This file adds the necessary compatibility tricks to avoid symbols with
version GLIBCXX_3.4.20 and bigger, keeping binary compatibility with
libstdc++ 4.8.1.
WARNING: all symbols from this file must be defined weak when they
overlap with libstdc++.
namespace std {
/* We shouldn't be throwing exceptions at all, but it sadly turns out
we call STL (inline) functions that do. This avoids the GLIBCXX_3.4.20
symbol version. */
void __attribute__((weak)) __throw_out_of_range_fmt(char const* fmt, ...) {
va_list ap;
char buf[1024]; // That should be big enough.
va_start(ap, fmt);
vsnprintf(buf, sizeof(buf), fmt, ap);
buf[sizeof(buf) - 1] = 0;
} // namespace std
namespace __cxxabiv1 {
/* Calls to this function are added by the compiler itself on `new Class[n]`
* calls. This avoids the GLIBCXX_3.4.20 symbol version. */
extern "C" void __attribute__((weak)) __cxa_throw_bad_array_new_length() {
} // namespace __cxxabiv1
namespace std {
/* This avoids the GLIBCXX_3.4.29 symbol version. */
void __attribute__((weak)) __throw_bad_array_new_length() { MOZ_CRASH(); }
} // namespace std
/* While we generally don't build with exceptions, we have some host tools
* that do use them. libstdc++ from GCC 5.0 added exception constructors with
* char const* argument. Older versions only have a constructor with
* std::string. This avoids the GLIBCXX_3.4.21 symbol version. */
namespace std {
__attribute__((weak)) runtime_error::runtime_error(char const* s)
: runtime_error(std::string(s)) {}
__attribute__((weak)) out_of_range::out_of_range(char const* s)
: out_of_range(std::string(s)) {}
__attribute__((weak)) invalid_argument::invalid_argument(char const* s)
: invalid_argument(std::string(s)) {}
} // namespace std
/* Expose the definitions for the old ABI, allowing us to call its functions */
#include <thread>
namespace std {
/* The old ABI has a thread::_M_start_thread(shared_ptr<_Impl_base>),
* while the new has thread::_M_start_thread(unique_ptr<_State>, void(*)()).
* There is an intermediate ABI at version 3.4.21, with
* thread::_M_start_thread(shared_ptr<_Impl_base>, void(*)()).
* The void(*)() parameter is only there to keep a reference to pthread_create
* on the caller side, and is unused in the implementation
* We're creating an entry point for the new and intermediate ABIs, and make
* them call the old ABI. This avoids the GLIBCXX_3.4.21 symbol version. */
__attribute__((weak)) void thread::_M_start_thread(shared_ptr<_Impl_base> impl,
void (*)()) {
/* We need a _Impl_base-derived class wrapping a _State to call the old ABI
* from what we got by diverting the new API. This avoids the GLIBCXX_3.4.22
* symbol version. */
struct StateWrapper : public thread::_Impl_base {
unique_ptr<thread::_State> mState;
StateWrapper(unique_ptr<thread::_State> aState) : mState(std::move(aState)) {}
void _M_run() override { mState->_M_run(); }
/* This avoids the GLIBCXX_3.4.22 symbol version. */
__attribute__((weak)) void thread::_M_start_thread(unique_ptr<_State> aState,
void (*)()) {
auto impl = std::make_shared<StateWrapper>(std::move(aState));
/* For some reason this is a symbol exported by new versions of libstdc++,
* even though the destructor is default there too. This avoids the
* GLIBCXX_3.4.22 symbol version. */
__attribute__((weak)) thread::_State::~_State() = default;
// Ideally we'd define
// bool _Sp_make_shared_tag::_S_eq(const type_info& ti) noexcept
// but we wouldn't be able to change its visibility because of the existing
// definition in C++ headers. We do need to change its visibility because we
// don't want it to be shadowing the one provided by libstdc++ itself, because
// it doesn't support RTTI. Not supporting RTTI doesn't matter for Firefox
// itself because it's built with RTTI disabled.
// So we define via the mangled symbol.
// This avoids the GLIBCXX_3.4.26 symbol version.
extern "C" __attribute__((visibility("hidden"))) bool
_ZNSt19_Sp_make_shared_tag5_S_eqERKSt9type_info(const type_info*) noexcept {
return false;
} // namespace std
namespace std {
/* Instantiate this template to avoid GLIBCXX_3.4.21 symbol versions
* depending on optimization level */
template basic_ios<char, char_traits<char>>::operator bool() const;
} // namespace std
#if !defined(MOZ_ASAN) && !defined(MOZ_TSAN)
/* operator delete with size is only available in CXXAPI_1.3.9, equivalent to
* GLIBCXX_3.4.21. */
void operator delete(void* ptr, size_t size) noexcept(true) {
::operator delete(ptr);
namespace std {
/* Instantiate this template to avoid GLIBCXX_3.4.23 symbol versions
* depending on optimization level */
template basic_string<char, char_traits<char>, allocator<char>>::basic_string(
const basic_string&, size_t, const allocator<char>&);
// This avoids the GLIBCXX_3.4.26 symbol version.
template basic_stringstream<char, char_traits<char>,
template basic_ostringstream<char, char_traits<char>,
// This avoids the GLIBCXX_3.4.29 symbol version.
template void basic_string<char, char_traits<char>, allocator<char>>::reserve();
template void
basic_string<wchar_t, char_traits<wchar_t>, allocator<wchar_t>>::reserve();
} // namespace std
/* The __cxa_thread_atexit_impl symbol is only available on GLIBC 2.18, but we
* want things to keep working on 2.17. It's not actually used directly from
* C++ code, but through __cxa_thead_atexit in libstdc++. The problem we have,
* though, is that rust's libstd also uses it, introducing a dependency we
* don't actually want. Fortunately, we can fall back to libstdc++'s wrapper
* (which, on systems without __cxa_thread_atexit_impl, has its own compatible
* implementation).
* The __cxa_thread_atexit symbol itself is marked CXXABI_1.3.7, which is
* equivalent to GLIBCXX_3.4.18.
extern "C" int __cxa_thread_atexit_impl(void (*dtor)(void*), void* obj,
void* dso_handle) {
return __cxxabiv1::__cxa_thread_atexit(dtor, obj, dso_handle);