}
snprintf(filename, sizeof(filename), "%s%s%s/memory.stat", cgroup, (per_ss ? "/memory" : ""), name);
- if ((fp = fopen(filename, "r")) == -1)
+ if ((fp = fopen(filename, "r")) == NULL)
perror("open(memory.stat)");
else {
unsigned long long _rss = 0, _mapped_file = 0;