[libcamera-devel] [PATCH 2/2] libcamera: pipeline: ipu3: Fix incorrect bdsHeight calculation

[Jean-Michel Hautbois]

Hi Laurent,

On 31/05/2021 04:07, Laurent Pinchart wrote:
> When compiling with optimization, gcc 9 and newer throw an unitialized
> variable warning:
> 
> ../../src/libcamera/pipeline/ipu3/imgu.cpp: In function ‘void libcamera::{anonymous}::calculateBDSHeight(libcamera::ImgUDevice::Pipe*, const libcamera::Size&, const libcamera::Size&, unsigned int, float)’:
> ../../src/libcamera/pipeline/ipu3/imgu.cpp:172:17: error: ‘bdsHeight’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
>   172 |    unsigned int bdsIntHeight = static_cast<unsigned int>(bdsHeight);
> 
> Neither clang not gcc versions older than 9 complain. This seems to be
> a false positive.
> 
> However, there's an obvious error in the code. The second while () loop
> in the first part of calculateBDSHeight() modifies the bdsHeight
> variable set by the first loop even if the second loop doesn't find a
> suitable height. This can result in an incorrect bdsHeight value. Fix
> this, which also gets rid of the compiler warning.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
Tested-by: Jean-Michel Hautbois <jeanmichel.hautbois at ideasonboard.com>
Reviewed-by: Jean-Michel Hautbois <jeanmichel.hautbois at ideasonboard.com>
> ---
>  src/libcamera/pipeline/ipu3/imgu.cpp | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/src/libcamera/pipeline/ipu3/imgu.cpp b/src/libcamera/pipeline/ipu3/imgu.cpp
> index 3e517ac67962..4eb3f7b730a9 100644
> --- a/src/libcamera/pipeline/ipu3/imgu.cpp
> +++ b/src/libcamera/pipeline/ipu3/imgu.cpp
> @@ -138,12 +138,13 @@ void calculateBDSHeight(ImgUDevice::Pipe *pipe, const Size &iif, const Size &gdc
>  		while (ifHeight >= minIFHeight && ifHeight <= iif.height &&
>  		       ifHeight / bdsSF >= minBDSHeight) {
>  
> -			bdsHeight = ifHeight / bdsSF;
> -			if (std::fmod(bdsHeight, 1.0) == 0) {
> -				unsigned int bdsIntHeight = static_cast<unsigned int>(bdsHeight);
> +			float height = ifHeight / bdsSF;
> +			if (std::fmod(height, 1.0) == 0) {
> +				unsigned int bdsIntHeight = static_cast<unsigned int>(height);
>  
>  				if (!(bdsIntHeight % BDS_ALIGN_H)) {
>  					foundIfHeight = ifHeight;
> +					bdsHeight = height;
>  					break;
>  				}
>  			}
> @@ -155,12 +156,13 @@ void calculateBDSHeight(ImgUDevice::Pipe *pipe, const Size &iif, const Size &gdc
>  		while (ifHeight >= minIFHeight && ifHeight <= iif.height &&
>  		       ifHeight / bdsSF >= minBDSHeight) {
>  
> -			bdsHeight = ifHeight / bdsSF;
> -			if (std::fmod(bdsHeight, 1.0) == 0) {
> -				unsigned int bdsIntHeight = static_cast<unsigned int>(bdsHeight);
> +			float height = ifHeight / bdsSF;
> +			if (std::fmod(height, 1.0) == 0) {
> +				unsigned int bdsIntHeight = static_cast<unsigned int>(height);
>  
>  				if (!(bdsIntHeight % BDS_ALIGN_H)) {
>  					foundIfHeight = ifHeight;
> +					bdsHeight = height;
>  					break;
>  				}
>  			}
>