poll(2) doesn't detect POLLHUP when events is 0
Originator: | shea | ||
Number: | rdar://37537852 | Date Originated: | February 14 2018 |
Status: | Open | Resolved: | |
Product: | macOS + SDK | Product Version: | |
Classification: | Bug | Reproducible: | Yes |
If the .events field of a struct pollfd is 0, poll(2) doesn't detect POLLHUP on that fd. Test case demonstrating the bug: #include <sys/types.h> #include <unistd.h> #include <poll.h> #include <stdio.h> #include <sys/wait.h> int monitor_process(int fd, short events) { struct pollfd spec = { .fd = fd, .events = events }; int res = poll(&spec, 1, 5 /* seconds */ * 1000 /* milliseconds/second */); switch (res) { case -1: perror("waiting for events"); return 1; case 0: fprintf(stderr, "poll timed out\n"); return 1; default: return 0; } } int go(short events) { int pipe_fds[2]; if (pipe(pipe_fds) == -1) { perror("making a pipe"); return 1; } pid_t child = fork(); switch (child) { case -1: perror("forking"); return 1; case 0: close(pipe_fds[1]); _exit(monitor_process(pipe_fds[0], events)); } close(pipe_fds[0]); close(pipe_fds[1]); int status; waitpid(child, &status, 0); if (WIFSIGNALED(status)) { fprintf(stderr, "child process died with signal: %d", WTERMSIG(status)); return 1; } int ret = WEXITSTATUS(status); if (ret != 0) fprintf(stderr, "child process failed with status %d, POLLHUP %s specified\n", ret, events & POLLHUP ? "is" : "is not"); return WEXITSTATUS(status); } int main(int argc, char ** argv) { int res0 = go(POLLHUP); int res1 = go(0); return res1 + res0; }
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