[libcamera-devel] [PATCH] libcamera: base: shared_fd: Don't dup() an invalid fd

[Kieran Bingham]

Quoting Laurent Pinchart (2021-12-06 14: 07:01)
> The SharedFD: :dup() implementation calls the C library dup() function on
Date: Mon, 06 Dec 2021 15:26:27 +0000
Message-ID: <163880438747.995700.268589314019276531 at Monstersaurus>
User-Agent: alot/0.10

> the fd. When the SharedFD instance is invalid, this produces an invalid
> fd, which is the correct behaviour, but logs an error message.

Isn't logging an error in that event a reasonable thing to do?

> Fix it by returning an invalid UniqueFD directly when the SharedFD is
> invalid. This also saves a system call, which is always nice to do.

Saving that seems worthwhile anyway as we know it won't succeed.

Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>

> Fixes: fcf98514cb4e ("libcamera: base: file_descriptor: Return UniqueFD from dup()")
> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> ---
>  src/libcamera/base/shared_fd.cpp | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/src/libcamera/base/shared_fd.cpp b/src/libcamera/base/shared_fd.cpp
> index bd2ab5aa25b7..c711cf579a04 100644
> --- a/src/libcamera/base/shared_fd.cpp
> +++ b/src/libcamera/base/shared_fd.cpp
> @@ -253,6 +253,9 @@ SharedFD &SharedFD::operator=(SharedFD &&other)
>   */
>  UniqueFD SharedFD::dup() const
>  {
> +       if (!isValid())
> +               return {};
> +
>         UniqueFD dupFd(::dup(get()));
>         if (!dupFd.isValid()) {
>                 int ret = -errno;
> 
> base-commit: f8d2f17a3db5ac490d7b505253a98d6795c2b630
> -- 
> Regards,
> 
> Laurent Pinchart
>