[libcamera-devel] [PATCH] libcamera: Remove std::piecewise_construct where not necessary

[Niklas Söderlund]

Hi Laurent,

Thanks for your patch.

On 2020-01-14 22:14:52 +0200, Laurent Pinchart wrote:
> When emplacing an element in a std::map, std::piecewise_construct is
> required to forward the parameters to the constructors of the key and
> mapped type, respectively. However, when the caller already has an
> instance of the mapped type, forwarding it to the mapped type copy
> constructor isn't really required, as the copy constructor would be
> called anyway. Drop std::piecewise_construct in those cases. This does
> not incur any performance cost.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

Reviewed-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>

> ---
>  src/libcamera/pipeline/uvcvideo.cpp | 4 +---
>  src/libcamera/pipeline/vimc.cpp     | 4 +---
>  2 files changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/src/libcamera/pipeline/uvcvideo.cpp b/src/libcamera/pipeline/uvcvideo.cpp
> index 83093676ec73..29afb121aa46 100644
> --- a/src/libcamera/pipeline/uvcvideo.cpp
> +++ b/src/libcamera/pipeline/uvcvideo.cpp
> @@ -365,9 +365,7 @@ int UVCCameraData::init(MediaEntity *entity)
>  			continue;
>  		}
>  
> -		ctrls.emplace(std::piecewise_construct,
> -			      std::forward_as_tuple(id),
> -			      std::forward_as_tuple(range));
> +		ctrls.emplace(id, range);
>  	}
>  
>  	controlInfo_ = std::move(ctrls);
> diff --git a/src/libcamera/pipeline/vimc.cpp b/src/libcamera/pipeline/vimc.cpp
> index c99560a45cfa..b1054d307ea2 100644
> --- a/src/libcamera/pipeline/vimc.cpp
> +++ b/src/libcamera/pipeline/vimc.cpp
> @@ -448,9 +448,7 @@ int VimcCameraData::init(MediaDevice *media)
>  			continue;
>  		}
>  
> -		ctrls.emplace(std::piecewise_construct,
> -			      std::forward_as_tuple(id),
> -			      std::forward_as_tuple(range));
> +		ctrls.emplace(id, range);
>  	}
>  
>  	controlInfo_ = std::move(ctrls);
> -- 
> Regards,
> 
> Laurent Pinchart
> 
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-- 
Regards,
Niklas Söderlund