[RFC PATCH v2/TEST CASE]

[Mauricio Faria de Oliveira <mfo@xxxxxxxxxxxxx>]

#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

#include <sys/mman.h>

int main() {
	int fd, rc;
	char *addr;
	const int PAGE_SIZE = sysconf(_SC_PAGESIZE);

	rc = unlink("file");
	if (rc < 0 && errno != ENOENT ) {
		perror("unlink");
		return 1;
	}

	fd = open("file", O_RDWR | O_CREAT, S_IRUSR | S_IWUSR);
	if (fd < 0) {
		perror("open");
		return 1;
	}

	addr = mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
	if (addr < 0) {
		perror("mmap");
		return 1;
	}

	rc = pwrite(fd, "a", 1, 0);
	if (rc < 0) {
		perror("pwrite");
		close(fd);
		return 1;
	}

	addr[0] = 'B';
	addr[1] = 'U';
	addr[2] = 'G';

	while (1) {
		printf("Press enter to change buffer contents\n");
		getchar();
		addr[3]++;
		printf("Buffer contents changed\n");
	}

	// This is not reached.
	rc = munmap(addr, PAGE_SIZE);
	if (rc < 0) {
		perror("munmap");
		return 1;
	}

	close(fd);
	return 0;
}