Re: [PATCH] return EBADF from ttyname_r

[Rich Felker <dalias@libc.org>]

On Wed, Sep 12, 2018 at 05:34:24PM -0700, Benjamin Peterson wrote:
> POSIX allows ttyname(_r) to return EBADF if passed file descriptor is invalid.
> ---
>  src/unistd/ttyname_r.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/src/unistd/ttyname_r.c b/src/unistd/ttyname_r.c
> index 33aa4ae1..e208b3c3 100644
> --- a/src/unistd/ttyname_r.c
> +++ b/src/unistd/ttyname_r.c
> @@ -10,7 +10,10 @@ int ttyname_r(int fd, char *name, size_t size)
>  	char procname[sizeof "/proc/self/fd/" + 3*sizeof(int) + 2];
>  	ssize_t l;
>  
> -	if (!isatty(fd)) return ENOTTY;
> +	if (!isatty(fd)) {
> +		if (errno == EBADF) return EBADF;
> +		return ENOTTY;
> +	}
>  
>  	__procfdname(procname, fd);
>  	l = readlink(procname, name, size);
> -- 
> 2.17.1

The EBADF error for isatty is optional and musl's does not set it, so
this patch does not work as-is. I think returning ENOTTY for cases for
which it does not apply in ttyname_r is non-conforming though, so
some change similar to this is probably needed. If isatty were
modified to set errno, I think we could just return errno here.

Rich