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libstdc++: Fix lifetime bugs for non-TLS eh_globals [PR105880]

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This ensures that the single-threaded fallback buffer eh_globals is not
destroyed during program termination, using the same immortalization
technique used for error category objects.

Also ensure that init._M_init can still be read after init has been
destroyed, by making it a static data member.

libstdc++-v3/ChangeLog:

	PR libstdc++/105880
	* libsupc++/eh_globals.cc (eh_globals): Ensure constant init and
	prevent destruction during termination.
	(__eh_globals_init::_M_init): Replace with static member _S_init.
	(__cxxabiv1::__cxa_get_globals_fast): Update.
	(__cxxabiv1::__cxa_get_globals): Likewise.
This commit is contained in:
Jonathan Wakely 2022-06-08 10:43:57 +01:00
parent 1753a71201
commit 1e65f2ed99
1 changed files with 37 additions and 14 deletions
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49
libstdc++-v3/libsupc++/eh_globals.cc
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@ -64,8 +64,26 @@ __cxxabiv1::__cxa_get_globals() _GLIBCXX_NOTHROW
#else
// Single-threaded fallback buffer.
static __cxa_eh_globals eh_globals;
#if __has_cpp_attribute(clang::require_constant_initialization)
# define __constinit [[clang::require_constant_initialization]]
#endif
namespace
{
struct constant_init
{
union {
unsigned char unused;
__cxa_eh_globals obj;
};
constexpr constant_init() : obj() { }
~constant_init() { /* do nothing, union member is not destroyed */ }
};
// Single-threaded fallback buffer.
__constinit constant_init eh_globals;
}
#if __GTHREADS
@ -90,32 +108,37 @@ eh_globals_dtor(void* ptr)
struct __eh_globals_init
{
__gthread_key_t _M_key;
bool _M_init;
static bool _S_init;
__eh_globals_init() : _M_init(false)
__eh_globals_init()
{
if (__gthread_active_p())
_M_init = __gthread_key_create(&_M_key, eh_globals_dtor) == 0;
_S_init = __gthread_key_create(&_M_key, eh_globals_dtor) == 0;
}
~__eh_globals_init()
{
if (_M_init)
if (_S_init)
__gthread_key_delete(_M_key);
_M_init = false;
_S_init = false;
}
__eh_globals_init(const __eh_globals_init&) = delete;
__eh_globals_init& operator=(const __eh_globals_init&) = delete;
};
bool __eh_globals_init::_S_init = false;
static __eh_globals_init init;
extern "C" __cxa_eh_globals*
__cxxabiv1::__cxa_get_globals_fast() _GLIBCXX_NOTHROW
{
__cxa_eh_globals* g;
if (init._M_init)
if (init._S_init)
g = static_cast<__cxa_eh_globals*>(__gthread_getspecific(init._M_key));
else
g = &eh_globals;
g = &eh_globals.obj;
return g;
}
@ -123,7 +146,7 @@ extern "C" __cxa_eh_globals*
__cxxabiv1::__cxa_get_globals() _GLIBCXX_NOTHROW
{
__cxa_eh_globals* g;
if (init._M_init)
if (init._S_init)
{
g = static_cast<__cxa_eh_globals*>(__gthread_getspecific(init._M_key));
if (!g)
@ -140,7 +163,7 @@ __cxxabiv1::__cxa_get_globals() _GLIBCXX_NOTHROW
}
}
else
g = &eh_globals;
g = &eh_globals.obj;
return g;
}
@ -148,11 +171,11 @@ __cxxabiv1::__cxa_get_globals() _GLIBCXX_NOTHROW
extern "C" __cxa_eh_globals*
__cxxabiv1::__cxa_get_globals_fast() _GLIBCXX_NOTHROW
{ return &eh_globals; }
{ return &eh_globals.obj; }
extern "C" __cxa_eh_globals*
__cxxabiv1::__cxa_get_globals() _GLIBCXX_NOTHROW
{ return &eh_globals; }
{ return &eh_globals.obj; }
#endif