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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
Notes: sideshowbarker 2024-07-19 10:46:44 +09:00 
Author: https://github.com/ADKaster
Commit: https://github.com/SerenityOS/serenity/commit/824bbc74622
Pull-request: https://github.com/SerenityOS/serenity/pull/894
2 changed files with 52 additions and 9 deletions
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43
Libraries/LibC/crt0.cpp
View File

@ -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;

18
Libraries/LibC/stdlib.cpp
View File

@ -106,14 +106,13 @@ static inline T strtol_impl(const char* nptr, char** endptr, int base)
extern "C" {
typedef void (*__atexit_handler)();
static int __atexit_handler_count = 0;
static __atexit_handler __atexit_handlers[32];
// Itanium C++ ABI methods defined in crt0.cpp
extern int __cxa_atexit(void (*function)(void*), void* paramter, void* dso_handle);
extern void __cxa_finalize(void* dso_handle);
void exit(int status)
{
for (int i = 0; i < __atexit_handler_count; ++i)
__atexit_handlers[i]();
__cxa_finalize(nullptr);
extern void _fini();
_fini();
fflush(stdout);
@ -122,11 +121,14 @@ void exit(int status)
ASSERT_NOT_REACHED();
}
static void __atexit_to_cxa_atexit(void* handler)
{
reinterpret_cast<void (*)()>(handler)();
}
int atexit(void (*handler)())
{
ASSERT(__atexit_handler_count < 32);
__atexit_handlers[__atexit_handler_count++] = handler;
return 0;
return __cxa_atexit(__atexit_to_cxa_atexit, (void*)handler, nullptr);
}
void abort()