[newlib-cygwin/main] posix_spawn_file_actions_addfchdir_np: return EBADF on negative fd

[Corinna Vinschen <corinna@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=3124d8b436a8130130ffe9c6a397556ff0125e66

commit 3124d8b436a8130130ffe9c6a397556ff0125e66
Author:     Corinna Vinschen <corinna@vinschen.de>
AuthorDate: Wed Apr 19 20:48:14 2023 +0200
Commit:     Corinna Vinschen <corinna@vinschen.de>
CommitDate: Wed Apr 19 20:48:14 2023 +0200

    posix_spawn_file_actions_addfchdir_np: return EBADF on negative fd
    
    FreeBSD and Musl implement posix_spawn_file_actions_addfchdir_np
    so that it checks the incoming descriptor for being negative, and,
    if so, return with EBADF.  The POSIX proposal defining
    posix_spawn_file_actions_addfchdir follows this behaviour, see
    https://www.austingroupbugs.net/view.php?id=1208
    
    Fixes: 7e03fc35f528 ("Add posix_spawn_file_actions_add{f}chdir_np")
    Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

Diff:
---
 newlib/libc/posix/posix_spawn.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/newlib/libc/posix/posix_spawn.c b/newlib/libc/posix/posix_spawn.c
index 3506b0f8bffe..6fd6159d054d 100644
--- a/newlib/libc/posix/posix_spawn.c
+++ b/newlib/libc/posix/posix_spawn.c
@@ -565,7 +565,12 @@ posix_spawn_file_actions_addfchdir_np (
 	int fd)
 {
 	posix_spawn_file_actions_entry_t *fae;
-	int error;
+
+	/* POSIX proposal documents it as implemented in FreeBSD and Musl.
+	   Return EBADF if fd is negative.
+	   https://www.austingroupbugs.net/view.php?id=1208 */
+	if (fd < 0)
+		return EBADF;
 
 	/* Allocate object */
 	fae = malloc(sizeof(posix_spawn_file_actions_entry_t));