get_pid_max: Return maximum value for pid_t type when reading fails

src/util.c

@@ -94,22 +94,26 @@ int get_ncpu(void)
     return cached_ncpu;
 }
 
+#define MAX_INT_TYPE(type) \
+    ((type) ~((type)1 << (sizeof(type) * 8 - 1)))
+
 pid_t get_pid_max(void)
 {
 #if defined(__linux__)
-    long pid_max = -1;
-    FILE *fd;
-    if ((fd = fopen("/proc/sys/kernel/pid_max", "r")) == NULL)
+    long pid_max;
+    FILE *fp;
+    if ((fp = fopen("/proc/sys/kernel/pid_max", "r")) == NULL)
     {
         fprintf(stderr, "Fail to open /proc/sys/kernel/pid_max\n");
-        return (pid_t)-1;
+        return MAX_INT_TYPE(pid_t);
     }
-    if (fscanf(fd, "%ld", &pid_max) != 1)
+    if (fscanf(fp, "%ld", &pid_max) != 1)
     {
         fprintf(stderr, "Fail to read /proc/sys/kernel/pid_max\n");
-        pid_max = -1;
+        fclose(fp);
+        return MAX_INT_TYPE(pid_t);
     }
-    fclose(fd);
+    fclose(fp);
     return (pid_t)pid_max;
 #elif defined(__FreeBSD__)
     return (pid_t)99998;