[PATCH] rpi: Use alloca instead of variable length arrays

[Barnabás Pőcze]

Hi


2024. február 21., szerda 3:46 keltezéssel, Khem Raj <raj.khem at gmail.com> írta:

> Clang-18+ diagnoses this as error
> 
> | ../git/src/ipa/rpi/controller/rpi/alsc.cpp:499:10: error: variable length arrays in C++ are a Clang extension [-Werror,-Wvla-cxx-extension]     |   499 |         int xLo[X], xHi[X];
> |       |                 ^
> 
> Signed-off-by: Khem Raj <raj.khem at gmail.com>
> ---
>  src/ipa/rpi/controller/rpi/alsc.cpp | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/src/ipa/rpi/controller/rpi/alsc.cpp b/src/ipa/rpi/controller/rpi/alsc.cpp
> index 8a205c60..8c0ae8eb 100644
> --- a/src/ipa/rpi/controller/rpi/alsc.cpp
> +++ b/src/ipa/rpi/controller/rpi/alsc.cpp
> @@ -496,8 +496,8 @@ void resampleCalTable(const Array2D<double> &calTableIn,
>  	 * Precalculate and cache the x sampling locations and phases to save
>  	 * recomputing them on every row.
>  	 */
> -	int xLo[X], xHi[X];
> -	double xf[X];
> +	int *xLo = (int*)alloca(X), *xHi = (int*)alloca(X);
> +	double *xf = (double*)alloca(X);
>  	double scaleX = cameraMode.sensorWidth /
>  			(cameraMode.width * cameraMode.scaleX);
>  	double xOff = cameraMode.cropX / (double)cameraMode.sensorWidth;
> --
> 2.43.2


This change is incorrect, the allocated sizes are insufficient. Also I am not
sure going from VLA to alloca is really an improvement. Maybe the warning should
be turned off. Or dynamic stack allocation should be eliminated altogether.


Regards,
Barnabás Pőcze