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

[Hirokazu Honda]

Hi Laurent, thank you for the patch.

On Mon, May 31, 2021 at 11:08 AM Laurent Pinchart <
laurent.pinchart at ideasonboard.com> 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>
>

The fix looks correct to me.
Reviewed-by: Hirokazu Honda <hiroh at chromium.org>


> ---
>  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;
>                                 }
>                         }
> --
> Regards,
>
> Laurent Pinchart
>
>
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