[libcamera-devel] [PATCH v2] libcamera: Declare dependency on generated headers

[Laurent Pinchart]

Hi Kieran,

Thank you for the patch.

On Fri, Mar 06, 2020 at 05:20:30PM +0000, Kieran Bingham wrote:
> The control headers are generated automatically by parsing our YAML
> descriptions, and creating the control headers.
> 
> The headers for the controls can be used directly from within libcamera
> internal pipeline handlers and core components, but there is no link to
> ensure that the headers are generated before they are used.
> 
> As part of updating controls to support properties, the commit
> f870591a9bf5 ("libcamera: properties: Add location property") also
> inadvertently moved the generated headers out of the libcamera_api
> dependency generation.
> 
> This allowed a race condition to occur in builds where objects are
> attempted to be built before the API definitions had been generated.
> 
> Declare a dependency on the headers for libcamera to ensure that they
> are built before compiling any object within the libcamera library, and
> re-introduce the headers to the libcamera_api variable.

This is bundling two changes in one patch, and given the very low
probability of hitting the race, and unsuccessful past attempts to fix
it, I would prefer decoupling the two.

Would you be fine with the first patch carrying the libcamera_api change
only, with the Fixes: line, and the above paragraph removed, and a
second patch that adds the declary_dependency ? It would allow testing
the two independently.

> Fixes: f870591a9bf5 ("libcamera: properties: Add location property")
> 
> Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> ---
>  include/libcamera/meson.build | 2 ++
>  src/libcamera/meson.build     | 1 +
>  2 files changed, 3 insertions(+)
> 
> diff --git a/include/libcamera/meson.build b/include/libcamera/meson.build
> index f47c583cbbc0..88edf620f69e 100644
> --- a/include/libcamera/meson.build
> +++ b/include/libcamera/meson.build
> @@ -44,6 +44,8 @@ foreach header : control_source_files
>                                       install_dir : join_paths('include', include_dir))
>  endforeach
>  
> +libcamera_api += control_headers
> +
>  gen_header = files('gen-header.sh')
>  
>  libcamera_h = custom_target('gen-header',
> diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build
> index 88658ac563f7..cd95fa11534a 100644
> --- a/src/libcamera/meson.build
> +++ b/src/libcamera/meson.build
> @@ -97,6 +97,7 @@ libcamera_deps = [
>      cc.find_library('dl'),
>      libudev,
>      dependency('threads'),
> +    declare_dependency(sources : [control_headers])
>  ]
>  
>  libcamera_link_with = []

-- 
Regards,

Laurent Pinchart