Observation on signal accumulation

main.c

#include <unistd.h>
#include <signal.h>
#include <assert.h>
#include <stdio.h>
#include <sys/wait.h>

void handle_sender(pid_t receiver) {
	for (int i = 0; i < 10; i++) {
		usleep(100);
		puts("Signal sent");
		kill(receiver, SIGUSR1);
	}
}

void sig_handler(int _) {
	(void)_;

	puts("Signal received");
	usleep(500);
	puts("Signal received [done]");
}

void handle_receiver(void) {
	signal(SIGUSR1, sig_handler);

	while (1) {
		pause();
	}
}

int main(void) {
	pid_t pid = fork();

	assert(pid != -1);

	if (pid) {
		int status;

		handle_sender(pid);
		waitpid(pid, &status, 0);
	}

	else {
		handle_receiver();
	}
}

output.sh-session

$ gcc ./main.c -o ./main && ./main
Signal sent
Signal received
Signal sent
Signal sent
Signal sent
Signal sent
Signal received [done]
Signal received
Signal sent
Signal sent
Signal sent
Signal received [done]
Signal received
Signal sent
Signal sent
Signal received [done]
Signal received
Signal received [done]