samples: make pidfd-metadata fail gracefully on older kernels
Initialize pidfd to an invalid descriptor, to fail gracefully on those kernels that do not implement CLONE_PIDFD and leave pidfd unchanged. Signed-off-by: Dmitry V. Levin <ldv@altlinux.org> Signed-off-by: Christian Brauner <christian@brauner.io>
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@ -83,7 +83,7 @@ static int pidfd_metadata_fd(pid_t pid, int pidfd)
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int main(int argc, char *argv[])
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{
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int pidfd = 0, ret = EXIT_FAILURE;
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int pidfd = -1, ret = EXIT_FAILURE;
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char buf[4096] = { 0 };
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pid_t pid;
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int procfd, statusfd;
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@ -91,7 +91,11 @@ int main(int argc, char *argv[])
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pid = pidfd_clone(CLONE_PIDFD, &pidfd);
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if (pid < 0)
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exit(ret);
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err(ret, "CLONE_PIDFD");
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if (pidfd == -1) {
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warnx("CLONE_PIDFD is not supported by the kernel");
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goto out;
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}
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procfd = pidfd_metadata_fd(pid, pidfd);
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close(pidfd);
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