musl/src/exit/abort.c

#include <stdlib.h>
#include <signal.h>
#include "syscall.h"
#include "pthread_impl.h"
#include "atomic.h"

_Noreturn void abort(void)
{
	raise(SIGABRT);
	__block_all_sigs(0);
	a_crash();
	raise(SIGKILL);
	_Exit(127);
}
initial check-in, version 0.5.0 2011-02-12 00:22:29 -05:00			`#include <stdlib.h>`
			`#include <signal.h>`
ensure that abort always works Per POSIX, "The abort() function shall cause abnormal process termination to occur, unless the signal SIGABRT is being caught and the signal handler does not return." If SIGABRT is blocked or if a signal handler is installed and does return, abort is still required to cause abnormal program termination. We cannot use a_crash() to do this, since a SIGILL handler could also be installed (and might even longjmp out of the abort, not expecting to be invoked from within abort), nor can we rely on resetting the signal handler and re-raising the signal (this has race conditions in multi-threaded programs). On the other hand, SIGKILL is a perfectly safe, unblockable way to obtain abnormal program termination, and it requires no ugly loop-and-retry logic. 2012-06-02 21:53:04 -04:00			`#include "syscall.h"`
improve abort fallback behavior when raising SIGABRT fails to terminate these changes still do not yield a fully-conforming abort, but they fix two known issues: - per POSIX, termination via SIGKILL is not "abnormal", but both ISO C and POSIX require abort to yield abnormal termination. - raising SIGKILL fails to do anything to pid 1 in some containers. now, the trapping instruction produced by a_crash() is expected to produce abnormal termination, without the risk of invoking a signal handler since SIGILL and SIGSEGV are blocked, and _Exit, which contains an infinite loop analogous to the one being removed from abort itself, is used as a last resort. this implementation still fails to produce an exit status as if the process terminated via SIGABRT in cases where SIGABRT is blocked or ignored, but fixing that is not easy; the obvious pseudo-solutions all have subtle race conditions where a concurrent fork or exec can expose incorrect signal state. 2016-07-03 17:42:05 -04:00			`#include "pthread_impl.h"`
			`#include "atomic.h"`
initial check-in, version 0.5.0 2011-02-12 00:22:29 -05:00
add _Noreturn function attribute, with fallback for pre-C11 GNUC 2012-09-06 23:12:27 -04:00			`_Noreturn void abort(void)`
initial check-in, version 0.5.0 2011-02-12 00:22:29 -05:00			`{`
			`raise(SIGABRT);`
improve abort fallback behavior when raising SIGABRT fails to terminate these changes still do not yield a fully-conforming abort, but they fix two known issues: - per POSIX, termination via SIGKILL is not "abnormal", but both ISO C and POSIX require abort to yield abnormal termination. - raising SIGKILL fails to do anything to pid 1 in some containers. now, the trapping instruction produced by a_crash() is expected to produce abnormal termination, without the risk of invoking a signal handler since SIGILL and SIGSEGV are blocked, and _Exit, which contains an infinite loop analogous to the one being removed from abort itself, is used as a last resort. this implementation still fails to produce an exit status as if the process terminated via SIGABRT in cases where SIGABRT is blocked or ignored, but fixing that is not easy; the obvious pseudo-solutions all have subtle race conditions where a concurrent fork or exec can expose incorrect signal state. 2016-07-03 17:42:05 -04:00			`__block_all_sigs(0);`
			`a_crash();`
ensure that abort always works Per POSIX, "The abort() function shall cause abnormal process termination to occur, unless the signal SIGABRT is being caught and the signal handler does not return." If SIGABRT is blocked or if a signal handler is installed and does return, abort is still required to cause abnormal program termination. We cannot use a_crash() to do this, since a SIGILL handler could also be installed (and might even longjmp out of the abort, not expecting to be invoked from within abort), nor can we rely on resetting the signal handler and re-raising the signal (this has race conditions in multi-threaded programs). On the other hand, SIGKILL is a perfectly safe, unblockable way to obtain abnormal program termination, and it requires no ugly loop-and-retry logic. 2012-06-02 21:53:04 -04:00			`raise(SIGKILL);`
improve abort fallback behavior when raising SIGABRT fails to terminate these changes still do not yield a fully-conforming abort, but they fix two known issues: - per POSIX, termination via SIGKILL is not "abnormal", but both ISO C and POSIX require abort to yield abnormal termination. - raising SIGKILL fails to do anything to pid 1 in some containers. now, the trapping instruction produced by a_crash() is expected to produce abnormal termination, without the risk of invoking a signal handler since SIGILL and SIGSEGV are blocked, and _Exit, which contains an infinite loop analogous to the one being removed from abort itself, is used as a last resort. this implementation still fails to produce an exit status as if the process terminated via SIGABRT in cases where SIGABRT is blocked or ignored, but fixing that is not easy; the obvious pseudo-solutions all have subtle race conditions where a concurrent fork or exec can expose incorrect signal state. 2016-07-03 17:42:05 -04:00			`_Exit(127);`
initial check-in, version 0.5.0 2011-02-12 00:22:29 -05:00			`}`