I have the following GLSL 1.30 vertex and pixel shaders:
* Vertex shader:
flat out vec4 triangleColor;
gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
gl_ClipVertex = gl_ModelViewMatrix * gl_Vertex;
triangleColor = vec4(1.0, 1.0, 0.0, 1.0);
* Fragment shader:
precision highp float;
flat in vec4 triangleColor;
gl_FragColor = gl_Color * triangleColor;
Compilation is OK but linking fails with error:
error: declarations for uniform `gl_ModelViewProjectionMatrix' have mismatching invariant qualifiers
Slightly different vertex shaders can produce the error:
error: declarations for shader input `gl_Vertex' have mismatching invariant qualifiers
There is no linking error anymore when I remove the "invariant gl_Position;" declaration.
Given that gl_Vertex and gl_ModelViewProjectionMatrix are not output variables for vertex shaders, I suppose that this behavior is not expected.
This error occurs with Mesa 17.0.2.
I ran into the same bug, on Ubuntu 17.04 with both Mesa 17.0.7-0ubuntu0.17.04.1 and 17.2.2+git20171019+17.2.23c08dab-0ubuntu0ricotz~17.04.1 (from the xorg-edgers ppa).
I have observed this bug both with Intel (Iris Pro 5200) and AMD (Radeon R7 370) GPUs.
It doesn't only happen with deprecated variables, but also when using a OpenGL core (3.2) context and corresponding shaders, by adding "invariant gl_Position;" to a vertex shader (doesn't seem to affect all vertex shaders, though).
It can be reproduced with this branch of Yamagi Quake2: https://github.com/DanielGibson/yquake2/tree/mesa-100316 (start with ./quake2 +set vid_renderer gl3)
The corresponding source is: https://github.com/DanielGibson/yquake2/blob/mesa-100316/src/client/refresh/gl3/gl3_shaders.c#L328-L329
(https://github.com/DanielGibson/yquake2/blob/mesa-100316/src/client/refresh/gl3/gl3_shaders.c#L261-L288 is also part of the shader)
When adding "invariant gl_Position;" into my simpler vertexSrc2D shader (https://github.com/DanielGibson/yquake2/blob/mesa-100316/src/client/refresh/gl3/gl3_shaders.c#L166), it does not create an error there.
As Olivier wrote, compiling the shader gives no errors, but linking the vertex- and fragment-shaders into a program fails.
The error message doesn't even mention gl_Position directly, but some other variable (in my case "error: declarations for uniform `transModel' have mismatching invariant qualifiers") - but when commenting the "invariant gl_Position;" line out, it works.
We're hitting the same issue with `invariant gl_Position;` (as described by Daniel in comment 1) in Godot Engine, at least for AMD hardware. Godot uses OpenGL 3.3 Core Profile: https://github.com/godotengine/godot/issues/13450
I've sent the patch for more general manifestation of the issue: https://patchwork.freedesktop.org/patch/247067/
(In reply to Danylo from comment #3)
> I've sent the patch for more general manifestation of the issue:
Just noting that Danylo submitted a merge request for this patch:
Fixed by Danylo in:
glsl: Cross validate variable's invariance by explicit invariance only