Bug 109524

I have had the same problem in Mesa 19.0.0 with the Nouveau driver.  It seems that any card without hardware shaders is failing.  This was tested with NV05 and NV11.

Connected to this bug report on WineHQ: https://bugs.winehq.org/show_bug.cgi?id=47389

Confirmed for Mesa 18.3.6. R100-class GPU too (ATI Mobility Radeon 7000 IGP).

R100 class Radeon GPUs only support OpenGL up to 1.3, while GLSL has only become a thing as an extension for 1.4 and finally an integral feature in 2.0. Does that mean OpenGL Shading Language support is nowadays necessary for Mesa?

Other applications using OpenGL (and so mesa, I guess?) still seem to work

NV05 and NV11 don't support GLSL at all. Some entry point must not be preventing it properly... perhaps something internal.

Is there like a wine test or something of the sort that can be used to reproduce this? I have such a GPU plugged in I can test with, but I need a repro.

(In reply to Ilia Mirkin from comment #5)

> Is there like a wine test or something of the sort that can be used to
> reproduce this? I have such a GPU plugged in I can test with, but I need a
> repro.

You can try this console emulator, it will crash on my old machine with the affected GPU:
http://fileland.square7.ch/t2k.zip

This patch should avoid the error being printed:

https://patchwork.freedesktop.org/patch/315751/

However I suspect that the calling code will continue to crash -- we return a NULL pointer, and I suspect that the caller expects this to be non-null.

Doing a little more digging, we enabled GL_ARB_shading_language_100 unconditionally in 2013:

commit 70966570f3e4275dc15b5a94c70698f6aef64150
Author: Ian Romanick <ian.d.romanick@intel.com>
Date:   Thu Jun 27 18:20:31 2013 -0700

    mesa: GL_ARB_shading_language_100 is not optional

However it appears that wine code has something like

https://source.winehq.org/git/wine.git/blob/201d13a3c31131f204f89d61be37bf75d58dc6dd:/dlls/wined3d/adapter_gl.c#l3737

3737     if (gl_info->supported[ARB_SHADING_LANGUAGE_100])
3738     {
3739         const char *str = (const char *)gl_info->gl_ops.gl.p_glGetString(GL_SHADING_LANGUAGE_VERSION_ARB);
3740         unsigned int major, minor;
3741 
3742         TRACE("GLSL version string: %s.\n", debugstr_a(str));
3743 
3744         /* The format of the GLSL version string is "major.minor[.release] [vendor info]". */
3745         sscanf(str, "%u.%u", &major, &minor);
3746         gl_info->glsl_version = MAKEDWORD_VERSION(major, minor);

I think the debugstr_a(NULL) is giving problems, but if it's not, sscanf probably will.

I'm not 100% sure who's right here. Certainly the GL_ARB_shading_language_100 spec talks about GL_SHADING_LANGUAGE_VERSION_ARB not being available due to it not existing in early extension specs. 

However the current behavior is a bit questionable on the mesa side. I don't know what the rationale was for always exposing the ext (as given, it's because one ought to check for ARB_vertex_program/etc, but that seems weak).

Note that the following patch makes the t2k thing that was attached work fine. However I need to check with Ian as to what's up.

diff --git a/src/mesa/main/extensions_table.h b/src/mesa/main/extensions_table.h
index 332a75e6c73..ec376e497df 100644
--- a/src/mesa/main/extensions_table.h
+++ b/src/mesa/main/extensions_table.h
@@ -135,7 +135,7 @@ EXT(ARB_shader_subroutine                   , dummy_true
 EXT(ARB_shader_texture_image_samples        , ARB_shader_texture_image_samples       , GLL, GLC,  x ,  x , 2014)
 EXT(ARB_shader_texture_lod                  , ARB_shader_texture_lod                 , GLL, GLC,  x ,  x , 2009)
 EXT(ARB_shader_viewport_layer_array         , ARB_shader_viewport_layer_array        , GLL, GLC,  x ,  x , 2015)
-EXT(ARB_shading_language_100                , dummy_true                             , GLL,  x ,  x ,  x , 2003)
+EXT(ARB_shading_language_100                , dummy_true                             , 15,  x ,  x ,  x , 2003)
 EXT(ARB_shading_language_420pack            , ARB_shading_language_420pack           , GLL, GLC,  x ,  x , 2011)
 EXT(ARB_shading_language_packing            , ARB_shading_language_packing           , GLL, GLC,  x ,  x , 2011)
 EXT(ARB_shadow                              , ARB_shadow                             , GLL,  x ,  x ,  x , 2001)

A better patch from Ian: https://patchwork.freedesktop.org/patch/315771/

(In reply to Ilia Mirkin from comment #10)
> A better patch from Ian: https://patchwork.freedesktop.org/patch/315771/

Thanks, this patch works on my machine.

On Debian Testing I still have Mesa 18.3.6; so do I have to build Mesa from source code in order to get the patch?

The patch landed in Mesa 19.1.5.

(In reply to Juan A. Suarez from comment #13)
> The patch landed in Mesa 19.1.5.

I meant 19.1.4. Sorry.

Thanks! I’ll wait until it gets committed to Debian repositories.