Re: Difficulty emulating F_DUPFD_CLOEXEC

[Rich Felker <dalias@aerifal.cx>]

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On Sat, Mar 23, 2013 at 09:59:23PM -0400, Rich Felker wrote:
> This uglifies fcntl.c a bit more, but I think it works. Does the above
> reasoning make sense? Any other ideas?

Proposed patch attached. Untested.

Rich

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diff --git a/src/fcntl/fcntl.c b/src/fcntl/fcntl.c
index fb7806a..3e7da2a 100644
--- a/src/fcntl/fcntl.c
+++ b/src/fcntl/fcntl.c
@@ -22,5 +22,17 @@ int fcntl(int fd, int cmd, ...)
 		if (ret) return __syscall_ret(ret);
 		return ex.type == F_OWNER_PGRP ? -ex.pid : ex.pid;
 	}
+	if (cmd == F_DUPFD_CLOEXEC) {
+		int ret = __syscall(SYS_fcntl, fd, F_DUPFD_CLOEXEC, arg);
+		if (ret != -EINVAL) return __syscall_ret(ret);
+		ret = __syscall(SYS_fcntl, fd, F_DUPFD_CLOEXEC, 0);
+		if (ret != -EINVAL) {
+			if (ret >= 0) __syscall(SYS_close, ret);
+			return __syscall_ret(-EINVAL);
+		}
+		ret = __syscall(SYS_fcntl, fd, F_DUPFD, arg);
+		if (ret >= 0) __syscall(SYS_fcntl, ret, F_SETFD, FD_CLOEXEC);
+		return __syscall_ret(ret);
+	}
 	return syscall(SYS_fcntl, fd, cmd, arg);
 }