1 files changed, 196 insertions, 0 deletions
diff --git a/build/unix/stdc++compat/stdc++compat.cpp b/build/unix/stdc++compat/stdc++compat.cpp
new file mode 100644
index 0000000000..0180f6bcfa
--- /dev/null
+++ b/build/unix/stdc++compat/stdc++compat.cpp
@@ -0,0 +1,196 @@
+/* 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 http://mozilla.org/MPL/2.0/. */
+
+#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;
+  va_end(ap);
+
+  __throw_range_error(buf);
+}
+
+}  // 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() {
+  MOZ_CRASH();
+}
+}  // namespace __cxxabiv1
+
+#if _GLIBCXX_RELEASE >= 11
+namespace std {
+
+/* This avoids the GLIBCXX_3.4.29 symbol version. */
+void __attribute__((weak)) __throw_bad_array_new_length() { MOZ_CRASH(); }
+
+}  // namespace std
+#endif
+
+/* 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 */
+#define _GLIBCXX_THREAD_ABI_COMPAT 1
+#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 (*)()) {
+  _M_start_thread(std::move(impl));
+}
+
+/* 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));
+  _M_start_thread(std::move(impl));
+}
+
+/* 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;
+
+#if _GLIBCXX_RELEASE >= 9
+// 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;
+}
+#endif
+
+}  // 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);
+}
+#endif
+
+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>&);
+
+#if _GLIBCXX_RELEASE >= 9
+// This avoids the GLIBCXX_3.4.26 symbol version.
+template basic_stringstream<char, char_traits<char>,
+                            allocator<char>>::basic_stringstream();
+
+template basic_ostringstream<char, char_traits<char>,
+                             allocator<char>>::basic_ostringstream();
+#endif
+
+#if _GLIBCXX_RELEASE >= 11
+// 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();
+#endif
+
+}  // 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);
+}