Re: [Buildroot] [PATCH 1/1] package/libpng: fix arm build

[Thomas Petazzoni via buildroot <buildroot@buildroot.org>]

Hello Bernd,

On Mon, 28 Oct 2024 20:39:15 +0100
Bernd Kuhls <bernd@kuhls.net> wrote:

> Bumping libpng to 1.6.44 with buildroot commit
> 583bb434ffe1eec0dbf6887dd719c3f41a6253e9
> causes a build failure on arm due to the upstream removal of
> the ASM implementation of ARM Neon optimizations.
> 
> Remove the corresponding configure options to fix the build error.
> 
> Fixes:
> http://autobuild.buildroot.net/results/021/02158525203d8c7f16a4a32637d44d6c87b7f333/
> 
> Signed-off-by: Bernd Kuhls <bernd@kuhls.net>
> ---
>  package/libpng/libpng.mk | 6 ------
>  1 file changed, 6 deletions(-)
> 
> diff --git a/package/libpng/libpng.mk b/package/libpng/libpng.mk
> index 3e7fc42d82..09b4494909 100644
> --- a/package/libpng/libpng.mk
> +++ b/package/libpng/libpng.mk
> @@ -17,12 +17,6 @@ HOST_LIBPNG_DEPENDENCIES = host-pkgconf host-zlib
>  LIBPNG_CONFIG_SCRIPTS = libpng$(LIBPNG_SERIES)-config libpng-config
>  LIBPNG_CONF_OPTS = --disable-tools
>  
> -ifeq ($(BR2_ARM_CPU_HAS_NEON)$(BR2_aarch64),y)
> -LIBPNG_CONF_OPTS += --enable-arm-neon
> -else
> -LIBPNG_CONF_OPTS += --disable-arm-neon
> -endif

Thanks for the research, but I'm afraid this fix is also not correct.
The NEON code has not been removed. What has been removed is the
assembly-written NEON code, but they still have NEON code that uses the
gcc intrinsics, that gets enabled by --enable-arm-neon.

However, this code is only available for softfp and hardfp ABIs, and
not soft-float. So the above condition should be changed to:

ifeq ($(BR2_aarch64),y)
LIBPNG_CONF_OPTS += --enable-arm-neon
else ifeq ($(BR2_ARM_CPU_HAS_NEON):$(BR2_ARM_SOFT_FLOAT),y:)
LIBPNG_CONF_OPTS += --enable-arm-neon
else
LIBPNG_CONF_OPTS += --disable-arm-neon
endif

should do the trick.

Thanks!

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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