Re: mesa@23.1.4: missing symbols

[John Kehayias]

Hi Sergio,

On Fri, Nov 03, 2023 at 06:05 PM, Sergio Pastor Pérez wrote:

> Hi.
>
> I've noticed that the `mesa' package we provide is missing some
> symbols that according to the OpenGL specification should be present on
> the `libGL.so.1` library.
>

I'll put the punchline up top with a few more details below. But the
symbol you want is in the libglvnd package:

--8<---------------cut here---------------start------------->8---
❯ nm -gD $(guix build libglvnd)/lib/libGL.so | grep glBindTextureUnit
000000000004cb60 T glBindTextureUnit
000000000004cb80 T glBindTextureUnitParameterEXT
--8<---------------cut here---------------end--------------->8---

> The following commands demonstrate the issue:
>
> $ guix build mesa
> /gnu/store/ds15k8bzqf1m861w17hshd8i54pffig9-mesa-23.1.4-bin
> /gnu/store/hxvp1sp897rnnpbpb0xk887m4822gf77-mesa-23.1.4
>
> $ nm -gD 
> /gnu/store/hxvp1sp897rnnpbpb0xk887m4822gf77-mesa-23.1.4/lib/libGL.so.1 | grep 
> glBindTextureUnit
>
> $ glxinfo | grep "OpenGL version"
> OpenGL version string: 4.6 (Compatibility Profile) Mesa 23.1.4
>
>

Indeed, I found this very puzzling as you did. I looked for other
symbols defined in the same Mesa headers and it was hit or miss
(mostly miss).

> As you can see the grep does not match any symbol. In contrast, if we do
> the same under an Ubuntu installation, we can see the following output:
>
> $ nm -gD /usr/lib/x86_64-linux-gnu/libGL.so.1 | grep glBindTextureUnit
> 0000000000046b60 T glBindTextureUnit
> 0000000000046b80 T glBindTextureUnitParameterEXT
>
> $ glxinfo | grep "OpenGL version"
> OpenGL version string: 4.6 (Compatibility Profile) Mesa 
> 23.0.4-0ubuntu1~22.04.1
>

I have a laptop with Arch on it and I saw the same thing you did on
Unbuntu. However, I decided to double check where libGL comes from and
it is owned not by the mesa package there but libglvnd! And that's how
I found libGL also in our libglvnd package with the symbol you were
looking for.

Unfortunately 'guix locate' didn't help me find other libGL in this
case (I tried that first) since I don't have libglvnd installed in any
profile. But a future upgrade or remote database of files in all our
packages will make this simpler.

>
> This symbol is also present on the `libGL.so.1` provided by the
> proprietary Nvidia driver:
>
> $ guix build nvidia-driver
> /gnu/store/8xhdq3rf9k80n6vz5cwi7z1dg5wjq002-nvidia-driver-515.76
>
> $ nm -gD 
> /gnu/store/8xhdq3rf9k80n6vz5cwi7z1dg5wjq002-nvidia-driver-515.76/lib/libGL.so.1
>  | grep glBindTextureUnit
> 00000000000476c0 T glBindTextureUnit
> 0000000000047700 T glBindTextureUnitParameterEXT
>
> $ glxinfo | grep "OpenGL version"
> OpenGL version string: 4.5 (Compatibility Profile) Mesa 23.1.4
>

Proprietary stuff aside, this comes back to a question raised before
for Guix that we haven't tackled, and that's libglvnd and loading
other gl drivers (yes, could be proprietary, but also more generally
on a foreign distro). Building mesa with libglvnd support is easy
enough, but the proper way to set this up to work well on Guix and
foreign systems I'm not so sure. It has been a while since I looked at
it but happy for someone to bring this up again or propose what we
should do to make it all work seamlessly. That's what libglvnd is for
after all, to dispatch gl calls to the right driver. (I think the idea
is that mesa is a provider of an implementation and the more general
top level for these symbols is elsewhere, libglvnd which could
dispatch it to mesa?)

> I've noticed the problem because I'm packaging a rust up that I wanted to
> contribute as an example on how to build applications that use meson to
> build rust packages. This app uses `rust-minidl' to load `libGL.so.1` at
> runtime. The app tries to use the `glBindTextureUnit` symbol and panics.
>
> Does anyone know why this symbol could be missing? Could we fix the
> `mesa' package? I would like users of the open source drivers to be able
> to run the package.
>
> Thanks,
> Sergio.


So the first thing is to use libglvnd in your packaging, which will
get you the symbol you need. Whether more is needed for this to work
properly (mesa input also or something else) I don't know. And if
other packages in Guix actually need libglvnd (and mesa) to work I
also don't know but I would guess comes up in a bug report if it does
happen.

Hope that helps! And I'm glad it wasn't some huge oversight in how we
build mesa (as far as I can tell) which left me scratching my head at
first.

John