+char *join(const char *x, ...) {
+ va_list ap;
+ size_t l;
+ char *r, *p;
+
+ va_start(ap, x);
+
+ if (x) {
+ l = strlen(x);
+
+ for (;;) {
+ const char *t;
+
+ t = va_arg(ap, const char *);
+ if (!t)
+ break;
+
+ l += strlen(t);
+ }
+ } else
+ l = 0;
+
+ va_end(ap);
+
+ r = new(char, l+1);
+ if (!r)
+ return NULL;
+
+ if (x) {
+ p = stpcpy(r, x);
+
+ va_start(ap, x);
+
+ for (;;) {
+ const char *t;
+
+ t = va_arg(ap, const char *);
+ if (!t)
+ break;
+
+ p = stpcpy(p, t);
+ }
+ } else
+ r[0] = 0;
+
+ return r;
+}
+
+bool is_main_thread(void) {
+ static __thread int cached = 0;
+
+ if (_unlikely_(cached == 0))
+ cached = getpid() == gettid() ? 1 : -1;
+
+ return cached > 0;
+}
+