// gcc -std=c11 -D_POSIX_SOURCE -o sigprocmask-exclusion sigprocmask-exclusion.c
// gcc -std=c11 -D_DEFAULT_SOURCE -o sigprocmask-exclusion sigprocmask-exclusion.c

// if defined than the original signal mask is restored(SIG_SETMASK); otherwise the signal is removed from the mask (SIG_UNBLOCK)
//#define option1

/* ... cfm 3
 kopie van origineel
 gewijzigd:
  - forbid, permit verwijderd (forbid en permit opgenomen in main() )
  - handlers: toevoeging en verwijdering van het andere signal
   - options: 1. either restore original mask (using SIG_SETMASK) or 2. removal signal from mask (using SIG_UNBLOCK)
   - 1st option fails after a long while, 2nd option fails mostly fails immediately
  - sigaction: het andere signal wordt niet verhinderd
 this test case fails on Cygwin; immediately when the 2nd option is used, after some time when the 1st option is used
 */

/*
 * Demonstrate improper delivery of a blocked signal.
 *
 * This program prints "ERROR: already forbidden" and aborts within one
 * second on this configuration (uname -srvm):
 *   CYGWIN_NT-10.0 2.7.0(0.306/5/3) 2017-02-12 13:18 x86_64
 *
 * It runs indefinitely (>600s) without trouble on these configurations:
 *   CYGWIN_NT-6.0 1.7.27(0.271/5/3) 2013-12-09 11:57 i686
 *   Linux 3.10.0-514.16.1.el7.x86_64 #1 SMP Wed Apr 12 15:04:24 UTC 2017 x86_64 [CentOS 7]
 *   AIX 7100-03-02-1412
 *   SunOS 5.10 Generic_147147-26 sun4u
 */

#include <setjmp.h>
#include <signal.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

static sigset_t block, unblock;
static char *stack_base;
static sigjmp_buf jmp;

static int cnt_usr1; static int cnt_chld = 0; static int cnt_int = 0;

static volatile sig_atomic_t i = 0;
static volatile sig_atomic_t j = 0;

static int r = 0;

static ptrdiff_t stack_usage_prev = 0;

/*
 * Start fresh in main() when the stack gets too deep.  This is not essential
 * to the test, but it allows for long runs without huge RLIMIT_STACK.
 */
static void
clear_stack_if_needed(void)
{
	char stack_position;
	ptrdiff_t stack_usage;

	stack_usage = stack_base - &stack_position;
	if (stack_usage < 0)
	{
		puts("NEGATIVE");
		stack_usage = -stack_usage;
	}

#if 0
if (stack_usage != stack_usage_prev) {
    printf("stack_usage: %d\n", stack_usage);
    stack_usage_prev = stack_usage;
}
#endif

	//if (stack_usage > 1024 * 1024)
	if (stack_usage > 5 * 1024) // 5 => 5120, 6 => 6144
	{
//sigprocmask(SIG_SETMASK, &block, NULL);
		puts("releasing excess stack");
//abort(); // if SA_NODEFER has been specified
		siglongjmp(jmp, 1);
	}
}

static void
handler(int arg)
{
	const char errmsg[] = "ERROR: handler: No 2 running\n";
	const char errmsg2[] = "ERROR: handler: nesting self!\n";

	sigset_t set, oset;
	r= sigemptyset(&set);
	r = sigaddset(&set, SIGCHLD);
	if (r != 0) puts("retvalH1");
	if (sigprocmask(SIG_BLOCK, &set, &oset) != 0) // voeg toe
		perror("sigprocmask");

	cnt_usr1++;
#if defined(__CYGWIN__)
{ sigset_t oset;
sigemptyset(&oset);
int rv = 0;
if (sigprocmask(SIG_BLOCK, NULL, &oset) != 0) // fetch current mask/ verify
	perror("sigprocmask");
if ( (rv = sigismember(&oset, SIGUSR1)) == -1)
	perror("sigismember");
if (rv == 0) puts ("handlerB: USR1 missing");
if ( (rv = sigismember(&oset, SIGCHLD)) == -1)
	perror("sigismember");
if (rv == 0) puts ("handlerB: CHLD missing");
}
#endif
//puts("H  ");
	if (i == 1) {
		write(2, errmsg2, sizeof(errmsg2) - 1);
printf("cnt_usr1 = %d, cnt_chld = %d, cnt_int = %d\n", cnt_usr1, cnt_chld, cnt_int); // not safe
		//abort();
	}
	if (j == 1) {
		write(2, errmsg, sizeof(errmsg) - 1);
// whoa, not shown ... ?????
printf("cnt_usr1 = %d, cnt_chld = %d, cnt_int = %d\n", cnt_usr1, cnt_chld, cnt_int); // not safe
		//abort();
	}
	i = 1;
	clear_stack_if_needed();
	usleep(5000);
	i = 0;
//puts("H-e   ");
#if defined(__CYGWIN__)
{ sigset_t oset;
sigemptyset(&oset);
int rv = 0;
if (sigprocmask(SIG_BLOCK, NULL, &oset) != 0) // fetch current mask/ verify
	perror("sigprocmask");
if ( (rv = sigismember(&oset, SIGUSR1)) == -1)
	perror("sigismember");
if (rv == 0) puts ("handlerE: USR1 missing");
if ( (rv = sigismember(&oset, SIGCHLD)) == -1)
	perror("sigismember");
if (rv == 0) puts ("handlerE: CHLD missing");
}
#endif

#if defined(option1)
	if (sigprocmask(SIG_SETMASK, &oset, NULL) != 0) // herstel
		perror("sigprocmask");
#else
	r = sigdelset(&set, SIGCHLD);
	if (r != 0) puts("retvalH1b");
	if (sigprocmask(SIG_UNBLOCK, &set, NULL) != 0) // verwijder
		perror("sigprocmask");
				  // Cygwin: aborts, almost immediately
#endif
}
static void
handler2(int arg)
{
	const char errmsg[] = "ERROR: handler2: No 1 running\n";
	const char errmsg2[] = "ERROR: handler2: nesting self!\n";

	sigset_t set, oset;
	r = sigemptyset(&set);
	r = sigaddset(&set, SIGUSR1);
	if (r != 0) puts("retvalH2");
	if (sigprocmask(SIG_BLOCK, &set, &oset) != 0) // voeg toe
		perror("sigprocmask");

	cnt_chld++;
#if defined(__CYGWIN__)
{ sigset_t oset;
sigemptyset(&oset);
int rv = 0;
if (sigprocmask(SIG_BLOCK, NULL, &oset) != 0) // fetch current mask/ verify
	perror("sigprocmask");
if ( (rv = sigismember(&oset, SIGUSR1)) == -1)
	perror("sigismember");
if (rv == 0) puts ("handler2B: USR1 missing");
if ( (rv = sigismember(&oset, SIGCHLD)) == -1)
	perror("sigismember");
if (rv == 0) puts ("handler2B: CHLD missing");
}
#endif
//puts("  H2");
	if (j == 1) {
		write(2, errmsg2, sizeof(errmsg2) - 1);
printf("cnt_usr1 = %d, cnt_chld = %d, cnt_int = %d\n", cnt_usr1, cnt_chld, cnt_int); // not safe
		//abort();
	}
	if (i == 1) {
		write(2, errmsg, sizeof(errmsg) - 1);
printf("cnt_usr1 = %d, cnt_chld = %d, cnt_int = %d\n", cnt_usr1, cnt_chld, cnt_int); // not safe
		//abort();
	}
	j = 1;
	clear_stack_if_needed();
	usleep(5000);
	j = 0;
//puts("  H2-e");
#if defined(__CYGWIN__)
{ sigset_t oset;
sigemptyset(&oset);
int rv = 0;
if (sigprocmask(SIG_BLOCK, NULL, &oset) != 0) // fetch current mask/ verify
	perror("sigprocmask");
if ( (rv = sigismember(&oset, SIGUSR1)) == -1)
	perror("sigismember");
if (rv == 0) puts ("handler2E: USR1 missing");
if ( (rv = sigismember(&oset, SIGCHLD)) == -1)
	perror("sigismember");
if (rv == 0) puts ("handler2E: CHLD missing");
}
#endif

#if defined(option1)
	if (sigprocmask(SIG_SETMASK, &oset, NULL) != 0) // herstel
		perror("sigprocmask");
#else
	r = sigdelset(&set, SIGUSR1);
	if (r != 0) puts("retvalH2b");
	if (sigprocmask(SIG_UNBLOCK, &set, NULL) != 0) // verwijder
		perror("sigprocmask");
#endif
}

#if 1
static void
handler3(int arg) // note: exhibits racing between bash and child
{
    cnt_int++;
    printf("cnt_usr1 = %d, cnt_chld = %d, cnt_int = %d\n", cnt_usr1, cnt_chld, cnt_int);
}
#endif

int main(int argc, char **argv)
{
	char stack_position;

	/* initial signal mask setup */
	r = sigemptyset(&unblock);

	r = sigfillset(&block);
	r = sigdelset(&block, SIGTRAP);
	r = sigdelset(&block, SIGABRT);
	r = sigdelset(&block, SIGILL);
	r = sigdelset(&block, SIGFPE);
	r = sigdelset(&block, SIGSEGV);
	r = sigdelset(&block, SIGBUS);
	r = sigdelset(&block, SIGSYS);
	r = sigdelset(&block, SIGCONT);
	if (r != 0) puts("retval0");

	if (sigprocmask(SIG_SETMASK, &block, NULL) != 0) // forbid
		perror("sigprocmask");

	/* Register signal handlers.  Problem somehow requires two signals. */
	{
		struct sigaction act, oact;

// the sa_mask is only applied during the execution of the handler

		act.sa_handler = handler;
		r = sigemptyset(&act.sa_mask); // however SIGUSR is auto added to mask during execution of the handler, is it not?
// do it in the handler
	//r = sigaddset(&act.sa_mask, SIGCHLD); // added
		if (r != 0) puts("retval1");
		act.sa_flags = 0;
		//act.sa_flags = SA_NODEFER; // be stupid
		if (sigaction(SIGUSR1, &act, &oact) != 0)
			perror("sigaction");

		struct sigaction act2, oact2;

		act2.sa_handler = handler2;
		r = sigemptyset(&act2.sa_mask);
	//r = sigaddset(&act2.sa_mask, SIGUSR1); // added
		if (r != 0) puts("retval2");
		act2.sa_flags = 0;
		//act2.sa_flags = SA_NODEFER; // be stupid
		if (sigaction(SIGCHLD, &act2, &oact2) != 0)
			perror("sigaction");

#if 1
struct sigaction act3, oact3;

act3.sa_handler = handler3;
r = sigfillset(&act3.sa_mask);
r = sigdelset(&act3.sa_mask, SIGINT); // remove
if (r != 0) puts("retval3");
act3.sa_flags = SA_RESETHAND;
if (sigaction(SIGINT, &act3, &oact3) != 0)
	perror("sigaction");
#endif
	}

	/* start a child to inundate me with signals */
	{
		pid_t pid, ppid;
		pid = fork();
		switch (pid)
		{
			case -1:
				perror("fork");
				return 1;
			case 0:
				ppid = getppid();
				printf("pid=%d inundating pid=%d with SIGUSR1 and SIGCHLD\n",
					   getpid(), ppid);
#if 0
				while (kill(ppid, random() % 2 ? SIGUSR1 : SIGCHLD) == 0)
					;
#else
volatile int i = 0;
//volatile int i = 1;
int xcnt_usr1 = 0; int xcnt_chld = 0;
while (1) {
    i = i ? 0 : 1;
    if (1) {
        if (kill(ppid, SIGCHLD) != 0) break;
        xcnt_chld++;
        if (kill(ppid, SIGUSR1) != 0) break; // LOST! WHY?
        xcnt_usr1++;
        if (kill(ppid, SIGUSR1) != 0) break; // LOST! WHY?
        xcnt_usr1++;
        if (kill(ppid, SIGCHLD) != 0) break;
        xcnt_chld++;
    } else {
        if (kill(ppid, SIGUSR1) != 0) break; // LOST! WHY?
        xcnt_usr1++;
        if (kill(ppid, SIGCHLD) != 0) break;
        xcnt_chld++;
        if (kill(ppid, SIGCHLD) != 0) break;
        xcnt_chld++;
        if (kill(ppid, SIGUSR1) != 0) break; // LOST! WHY?
        xcnt_usr1++;
    }
#if defined(__linux__)
    usleep(10000); // if disabled, either cnt_usr1 stays zero ?????
    // enabked: 2 : 1, disabled: 10.000 : 1
#endif           
#if defined(__CYGWIN__)
    //usleep(10000); // if disabled ...
    // using SIG_SETMASK (restore mask, saved at the start of the handler): ... abort, but after a long while (it seems)
    // using SIG_UNBLOCK: abort (almost immediately) ... Sigh!
#endif
}
#endif
				puts("child done");
printf("xcnt_usr1 = %d, xcnt_chld = %d\n", xcnt_usr1, xcnt_chld);
				return 0;
		}
	}

	/* loop forever while we receive signals */
	stack_base = &stack_position;
	sigsetjmp(jmp, 1);

	for (;;)
	{
puts("-");
		if (sigprocmask(SIG_SETMASK, &unblock, NULL) != 0) // permit
			perror("sigprocmask");
puts("--");
		usleep(1000);
puts("---");
		if (sigprocmask(SIG_SETMASK, &block, NULL) != 0) // forbid
			perror("sigprocmask");
puts("----");
	}
}