IOS development how to solve the capture signal handler by covering problems - ios

Question

I want to make both the existing singal handler in the project and my own singal handler co-exist so that both can properly capture singal.
typedef void (*signalHandler)(int signo, siginfo_t *info, void *context);
static signalHandler previousSignalHandler = NULL;
void signalExceptionHandler(int signal, siginfo_t* info, void* context)
{
NSMutableString *mstr = [[NSMutableString alloc] init];
[mstr appendString:#"Stack:\n"];
void* callstack[128];
int i, frames = backtrace(callstack, 128);
char** strs = backtrace_symbols(callstack, frames);
for (i = 0; i <frames; ++i) {
[mstr appendFormat:#"%s\n", strs[i]];
}
BYLOGI(#"%#",mstr);
[BYCrashCacheHelper saveAppCrashDataWithCrashInfo:mstr];
if (previousSignalHandler) {
previousSignalHandler(signal, info, context);
}
}
void signalRegister(int signal)
{
struct sigaction action;
action.sa_sigaction = signalExceptionHandler;
action.sa_flags = SA_NODEFER | SA_SIGINFO;
sigemptyset(&action.sa_mask);
sigaction(signal, &action, 0);
}
void judgePreviousSignalHandlerAndSignalRegister(int signal)
{
struct sigaction old_action;
sigaction(signal, NULL, &old_action);
if (old_action.sa_flags & SA_SIGINFO) {
previousSignalHandler = old_action.sa_sigaction;
}
signalRegister(signal);
}
void installSignalHandler(void)
{
judgePreviousSignalHandlerAndSignalRegister(SIGHUP);
judgePreviousSignalHandlerAndSignalRegister(SIGINT);
judgePreviousSignalHandlerAndSignalRegister(SIGQUIT);
judgePreviousSignalHandlerAndSignalRegister(SIGABRT);
judgePreviousSignalHandlerAndSignalRegister(SIGILL);
judgePreviousSignalHandlerAndSignalRegister(SIGSEGV);
judgePreviousSignalHandlerAndSignalRegister(SIGFPE);
judgePreviousSignalHandlerAndSignalRegister(SIGBUS);
judgePreviousSignalHandlerAndSignalRegister(SIGPIPE);
}
I found the above method in some blogs, but after debugging, I found that it can not get to the previous handler.
Excuse me, how to get the previous handler correctly, and avoid the handler coverage problem?