Re: [Imtoolkit-users] libpng link problem on Linux (Ubuntu 18.04 LTS)

[Antonio S. <ant...@gm...>]

  Hi,

  We don't link with libPNG because of GTK. Since it uses libPNG, if your
program uses GTK it already loads libPNG and it loads the correct lib
compatible with GTK.

  So if you don't use GTK, then you must explicitly link with  libPNG using
LIBS += png. It is not necessary to link with the version number. When the
libpng-dev package is installed a link is created to point to the file with
the version number.

Best,
Scuri


Em ter, 28 de mai de 2019 às 18:32, Matthew Kennedy <bur...@gm...>
escreveu:

> Hi,
>
> On Linux, it looks like the build system is designed to use the system
> libpng, but the resulting libim.so doesn't link against it:
>
> /tmp/im-3.13_Linux415_64_lib$ ldd libim.so
>         linux-vdso.so.1 (0x00007fff207bd000)
>         libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007f58218b4000)
>         libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6
> (0x00007f582152b000)
>         libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f582118d000)
>         libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1
> (0x00007f5820f75000)
>         libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f5820b84000)
>         /lib64/ld-linux-x86-64.so.2 (0x00007f5821e28000)
>
> #include <stdio.h>
> #include <dlfcn.h>
> int main(int argc, char **argv) {
>   void *result = dlopen(argv[1], RTLD_NOW);
>   if (! result) {
>     printf("error: %s\n", dlerror());
>   }
>   return 0;
> }
> // gcc -Wall -Werror testload.c -o testload -ldl
>
> /tmp/im-3.13_Linux415_64_lib$ ~/Projects/testload $PWD/libim.so
> error: /tmp/im-3.13_Linux415_64_lib/libim.so: undefined symbol:
> png_get_sRGB
>
> I also checked building from SVN and get the same result.
>
> I think where the build system is doing LIBS += png, it should do
> something like LIBS += png16 (at least on Ubuntu 18.04), but I'm not sure
> if that's legit for all distros.
>
> I can work around it by patching the libim.so shared object though:
>
> /tmp/im-3.13_Linux415_64_lib$ patchelf --add-needed libpng16.so.16 libim.so
> /tmp/im-3.13_Linux415_64_lib$ ~/Projects/testload $PWD/libim.so
>
> /tmp/im-3.13_Linux415_64_lib$ ldd libim.so
>         linux-vdso.so.1 (0x00007fffc4f4f000)
>         libpng16.so.16 => /usr/lib/x86_64-linux-gnu/libpng16.so.16
> (0x00007f0205a91000)
>         libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007f0205874000)
>         libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6
> (0x00007f02054eb000)
>         libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f020514d000)
>         libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1
> (0x00007f0204f35000)
>         libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f0204b44000)
>         /lib64/ld-linux-x86-64.so.2 (0x00007f0206022000)
>
> At this point, I can load the shared object (and invoke PNG related
> things, in Lisp, in my example):
>
> CL-USER> (im-file:image-load
> "/usr/share/backgrounds/Beaver_Wallpaper_Grey_4096x2304.png")
> #<TECGRAF-BASE:IM-IMAGE {100249FBB3}>
>
> The Windows builds do not have this problem.
>
> Matt
>
>
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