Re: [PATCH] gnu: Add optipng.

[Danny Milosavljevic]

Hi Leo,

On Mon, 26 Sep 2016 13:59:58 -0400
Leo Famulari <address@hidden> wrote:

> gcc -s -o optipng optipng.o optim.o bitset.o ratio.o osys.o wildargs.o 
> ../opngreduc/libopngreduc.a ../pngxtern/libpngxtern.a ../libpng/libpng.a 
> ../zlib/libz.a ../gifread/libgifread.a ../pnmio/libpnmio.a 
> ../minitiff/libminitiff.a   -lm 
> ../libpng/libpng.a(pngrutil.o): In function `png_read_filter_row':
> pngrutil.c:(.text+0x13bc): undefined reference to 
> `png_init_filter_functions_neon'
> collect2: error: ld returned 1 exit status
> make[1]: *** [Makefile:99: optipng] Error 1
> make[1]: Leaving directory 
> '/tmp/nix-build-optipng-0.7.6.drv-0/optipng-0.7.6/src/optipng'
> make: *** [Makefile:2: all] Error 2

Looks like a problem internal to libpng.

There's a configure option '--enable-arm-neon=api' in libpng. If we supported 
only ARM with NEON SIMD extension then we could build libpng with it. Do we?

Debian says on their https://wiki.debian.org/ArmHardFloatPort#NEON that one 
shouldn't require NEON since Marvell Dove and NVidia Tegra2 (?!?!?!) don't 
implement it.

There's also a configure option '--enable-arm-neon=check' which would check 
whether NEON works at runtime - but according to configure, it's not 
well-supported. What does this mean?