mem = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
if(mem == MAP_FAILED) {
xbt_die("Could not map fd %d: %s", fd, strerror(errno));
mem = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
if(mem == MAP_FAILED) {
xbt_die("Could not map fd %d: %s", fd, strerror(errno));