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Added workarounds for gcc < 4.7 on Linux and OpenBSD.

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Apparently, gcc < 4.7 on Linux also don't have __cxa_get_globals
declaration in cxxabi.h. Declare the function ourselves.

Also, on OpenBSD it seems there is no declaration either, and
on that platform the function implementation has no exception
specification, like on FreeBSD. Add a declaration of that platform.

Lastly, changed __cxa_get_globals and _getptd-based implementations
to avoid violating strict aliasing rules. This is still formally UB
to access structure fields like we do, but this is one less reason to
cause miscompilation or compiler warnings.
This commit is contained in:
Andrey Semashev
2019-01-08 00:23:09 +03:00
parent 9f9da9dc9b
commit dea6b04157
1 changed files with 23 additions and 7 deletions
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30
include/boost/core/uncaught_exceptions.hpp
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@ -49,25 +49,37 @@
#if !(defined(__MINGW32__) && (defined(__GNUC__) && (__GNUC__ * 100 + __GNUC_MINOR__) < 405))
#include <cxxabi.h>
// On Linux with clang and libc++, there is a version of cxxabi.h from libc++-abi that doesn't declare __cxa_get_globals, but provides __cxa_uncaught_exceptions.
// The function only appeared in version 1002.
// On Linux with clang and libc++, there is a version of cxxabi.h from libc++abi that doesn't declare __cxa_get_globals, but provides __cxa_uncaught_exceptions.
// The function only appeared in version 1002 of the library.
#if defined(_LIBCPPABI_VERSION) && _LIBCPPABI_VERSION >= 1002
#define BOOST_CORE_HAS_CXA_UNCAUGHT_EXCEPTIONS
#else
#include <cstring>
#define BOOST_CORE_HAS_CXA_GET_GLOBALS
// On MinGW only GCC 4.7 declares __cxa_get_globals() in cxxabi.h, older compilers do not expose this function but it's there.
// At least on MinGW and Linux, only GCC since 4.7 declares __cxa_get_globals() in cxxabi.h. Older versions of GCC do not expose this function but it's there.
// On OpenBSD, it seems, the declaration is also missing.
// Note that at least on FreeBSD 11, cxxabi.h declares __cxa_get_globals with a different exception specification, so we can't declare the function unconditionally.
#if (defined(__MINGW32__) && defined(__GNUC__) && (__GNUC__ * 100 + __GNUC_MINOR__) < 407) || defined(_LIBCPPABI_VERSION)
#if !defined(__FreeBSD__) && \
( \
(defined(__GNUC__) && (__GNUC__ * 100 + __GNUC_MINOR__) < 407) || \
defined(__OpenBSD__) || \
defined(_LIBCPPABI_VERSION) \
)
namespace __cxxabiv1 {
struct __cxa_eh_globals;
#if defined(__OpenBSD__)
extern "C" __cxa_eh_globals* __cxa_get_globals();
#else
extern "C" __cxa_eh_globals* __cxa_get_globals() BOOST_NOEXCEPT_OR_NOTHROW __attribute__((__const__));
#endif
} // namespace __cxxabiv1
#endif
#endif
#endif
#endif // !(defined(__MINGW32__) && (defined(__GNUC__) && (__GNUC__ * 100 + __GNUC_MINOR__) < 405))
#endif // defined(BOOST_CORE_HAS_CXXABI_H)
#if defined(_MSC_VER) && _MSC_VER >= 1400
#include <cstring>
#define BOOST_CORE_HAS_GETPTD
namespace boost {
namespace core {
@ -100,10 +112,14 @@ inline unsigned int uncaught_exceptions() BOOST_NOEXCEPT
return static_cast< unsigned int >(abi::__cxa_uncaught_exceptions());
#elif defined(BOOST_CORE_HAS_CXA_GET_GLOBALS)
// Tested on {clang 3.2,GCC 3.5.6,GCC 4.1.2,GCC 4.4.6,GCC 4.4.7}x{x32,x64}
return *(reinterpret_cast< const unsigned int* >(reinterpret_cast< const char* >(::abi::__cxa_get_globals()) + sizeof(void*))); // __cxa_eh_globals::uncaughtExceptions, x32 offset - 0x4, x64 - 0x8
unsigned int count;
std::memcpy(&count, reinterpret_cast< const unsigned char* >(::abi::__cxa_get_globals()) + sizeof(void*), sizeof(count)); // __cxa_eh_globals::uncaughtExceptions, x32 offset - 0x4, x64 - 0x8
return count;
#elif defined(BOOST_CORE_HAS_GETPTD)
// MSVC specific. Tested on {MSVC2005SP1,MSVC2008SP1,MSVC2010SP1,MSVC2012}x{x32,x64}.
return *(reinterpret_cast< const unsigned int* >(static_cast< const char* >(boost::core::detail::_getptd()) + (sizeof(void*) == 8 ? 0x100 : 0x90))); // _tiddata::_ProcessingThrow, x32 offset - 0x90, x64 - 0x100
unsigned int count;
std::memcpy(&count, static_cast< const unsigned char* >(boost::core::detail::_getptd()) + (sizeof(void*) == 8u ? 0x100 : 0x90), sizeof(count)); // _tiddata::_ProcessingThrow, x32 offset - 0x90, x64 - 0x100
return count;
#else
// Portable C++03 implementation. Does not allow to detect multiple nested exceptions.
return static_cast< unsigned int >(std::uncaught_exception());