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LibC: Support exit time destructors per the Itanium C++ ABI

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Implement __cxa_atexit and __cxa_finalize per the Itanium spec,
and convert stdlib's atexit and exit() to to call them instead of
a custom 'C-only' atexit implementation.
This commit is contained in:
Andrew Kaster 2019-12-21 15:49:29 -07:00 • committed by Andreas Kling
parent e2dcf27a2e
commit 824bbc7462
2 changed files with 52 additions and 9 deletions
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43
Libraries/LibC/crt0.cpp
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@ -49,8 +49,49 @@ int _start(int argc, char** argv, char** env)
ASSERT_NOT_REACHED();
}
void __cxa_atexit()
typedef void (*AtExitFunction)(void *);
struct __exit_entry
{
AtExitFunction method;
void* parameter;
void* dso_handle;
bool has_been_called;
};
static __exit_entry __exit_entries[1024]{};
static int __exit_entry_count = 0;
int __cxa_atexit(AtExitFunction exit_function, void *parameter, void *dso_handle)
{
if (__exit_entry_count >= 1024)
return -1;
__exit_entries[__exit_entry_count++] = { exit_function, parameter, dso_handle, false};
return 0;
}
void __cxa_finalize(void* dso_handle)
{
// From the itanium abi, https://itanium-cxx-abi.github.io/cxx-abi/abi.html#dso-dtor-runtime-api
//
// When __cxa_finalize(d) is called, it should walk the termination function list, calling each in turn
// if d matches __dso_handle for the termination function entry. If d == NULL, it should call all of them.
// Multiple calls to __cxa_finalize shall not result in calling termination function entries multiple times;
// the implementation may either remove entries or mark them finished.
int entry_index = __exit_entry_count;
while (--entry_index >= 0)
{
auto& exit_entry = __exit_entries[entry_index];
bool needs_calling = !exit_entry.has_been_called && (!dso_handle || dso_handle == exit_entry.dso_handle);
if (needs_calling) {
exit_entry.method(exit_entry.parameter);
exit_entry.has_been_called = true;
}
}
}
extern u32 __stack_chk_guard;