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greenlet_compiler_compat.hpp
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greenlet_compiler_compat.hpp
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/* -*- indent-tabs-mode: nil; tab-width: 4; -*- */
#ifndef GREENLET_COMPILER_COMPAT_HPP
#define GREENLET_COMPILER_COMPAT_HPP
/**
* Definitions to aid with compatibility with different compilers.
*
* .. caution:: Use extreme care with noexcept.
* Some compilers and runtimes, specifically gcc/libgcc/libstdc++ on
* Linux, implement stack unwinding by throwing an uncatchable
* exception, one that specifically does not appear to be an active
* exception to the rest of the runtime. If this happens while we're in a noexcept function,
* we have violated our dynamic exception contract, and so the runtime
* will call std::terminate(), which kills the process with the
* unhelpful message "terminate called without an active exception".
*
* This has happened in this scenario: A background thread is running
* a greenlet that has made a native call and released the GIL.
* Meanwhile, the main thread finishes and starts shutting down the
* interpreter. When the background thread is scheduled again and
* attempts to obtain the GIL, it notices that the interpreter is
* exiting and calls ``pthread_exit()``. This in turn starts to unwind
* the stack by throwing that exception. But we had the ``PyCall``
* functions annotated as noexcept, so the runtime terminated us.
*
* #2 0x00007fab26fec2b7 in std::terminate() () from /lib/x86_64-linux-gnu/libstdc++.so.6
* #3 0x00007fab26febb3c in __gxx_personality_v0 () from /lib/x86_64-linux-gnu/libstdc++.so.6
* #4 0x00007fab26f34de6 in ?? () from /lib/x86_64-linux-gnu/libgcc_s.so.1
* #6 0x00007fab276a34c6 in __GI___pthread_unwind at ./nptl/unwind.c:130
* #7 0x00007fab2769bd3a in __do_cancel () at ../sysdeps/nptl/pthreadP.h:280
* #8 __GI___pthread_exit (value=value@entry=0x0) at ./nptl/pthread_exit.c:36
* #9 0x000000000052e567 in PyThread_exit_thread () at ../Python/thread_pthread.h:370
* #10 0x00000000004d60b5 in take_gil at ../Python/ceval_gil.h:224
* #11 0x00000000004d65f9 in PyEval_RestoreThread at ../Python/ceval.c:467
* #12 0x000000000060cce3 in setipaddr at ../Modules/socketmodule.c:1203
* #13 0x00000000006101cd in socket_gethostbyname
*/
#include <cstdint>
# define G_NO_COPIES_OF_CLS(Cls) private: \
Cls(const Cls& other) = delete; \
Cls& operator=(const Cls& other) = delete
# define G_NO_ASSIGNMENT_OF_CLS(Cls) private: \
Cls& operator=(const Cls& other) = delete
# define G_NO_COPY_CONSTRUCTOR_OF_CLS(Cls) private: \
Cls(const Cls& other) = delete;
// CAUTION: MSVC is stupidly picky:
//
// "The compiler ignores, without warning, any __declspec keywords
// placed after * or & and in front of the variable identifier in a
// declaration."
// (https://docs.microsoft.com/en-us/cpp/cpp/declspec?view=msvc-160)
//
// So pointer return types must be handled differently (because of the
// trailing *), or you get inscrutable compiler warnings like "error
// C2059: syntax error: ''"
//
// In C++ 11, there is a standard syntax for attributes, and
// GCC defines an attribute to use with this: [[gnu:noinline]].
// In the future, this is expected to become standard.
#if defined(__GNUC__) || defined(__clang__)
/* We used to check for GCC 4+ or 3.4+, but those compilers are
laughably out of date. Just assume they support it. */
# define GREENLET_NOINLINE(name) __attribute__((noinline)) name
# define GREENLET_NOINLINE_P(rtype, name) rtype __attribute__((noinline)) name
# define UNUSED(x) UNUSED_ ## x __attribute__((__unused__))
#elif defined(_MSC_VER)
/* We used to check for && (_MSC_VER >= 1300) but that's also out of date. */
# define GREENLET_NOINLINE(name) __declspec(noinline) name
# define GREENLET_NOINLINE_P(rtype, name) __declspec(noinline) rtype name
# define UNUSED(x) UNUSED_ ## x
#endif
#if defined(_MSC_VER)
# define G_NOEXCEPT_WIN32 noexcept
#else
# define G_NOEXCEPT_WIN32
#endif
#if defined(__GNUC__) && defined(__POWERPC__) && defined(__APPLE__)
// 32-bit PPC/MacOSX. Only known to be tested on unreleased versions
// of macOS 10.6 using a macports build gcc 14. It appears that
// running C++ destructors of thread-local variables is broken.
// See https://github.com/python-greenlet/greenlet/pull/419
# define GREENLET_BROKEN_THREAD_LOCAL_CLEANUP_JUST_LEAK 1
#else
# define GREENLET_BROKEN_THREAD_LOCAL_CLEANUP_JUST_LEAK 0
#endif
#endif