Program undefined behavior warning

Gaming and Visualization Technologies APIs OpenGL
1

Our inhouse engine relies on angle to simulate GLES on PC. When running, we get the following warning from glDebugMessageCallback:

Message: Program undefined behavior warning: The current GL state uses a sampler (2) that has depth comparisons disabled, with a texture object (53) with a depth format, by a shader that samples it with a shadow sampler. Using this state to sample would result in undefined behavior.

I try figuring out what happened: At first I logged every texture unit & sampler, but find they seems correct with corresponding shader.

Then I guess maybe some texture unit/sampler are not cleared when not in use. After investigating angle’s StateManagerGL::updateProgramTextureBindings, I added some debug code in the end to force clean up

// test: force bind zero for inactive texture units
for (size_t textureUnitIndex = 0; textureUnitIndex < gl::IMPLEMENTATION_MAX_ACTIVE_TEXTURES;
     textureUnitIndex++)
{
    if (!activeTextures.test(textureUnitIndex))
    {
        activeTexture(textureUnitIndex);
        bindTexture(gl::TextureType::_3D, 0);
        bindTexture(gl::TextureType::_2DArray, 0);
        bindTexture(gl::TextureType::_2D, 0);
        bindSampler(textureUnitIndex, 0);
    }
}

Now I get similar warning but texture unit (0) and sampler (0)

Message: Program undefined behavior warning: The current GL state uses a sampler (0) that has depth comparisons disabled, with a texture object (0) with a non-depth format, by a shader that samples it with a shadow sampler. Using this state to sample would result in undefined behavior.

As I only cleanup inactive slots and all warning message changes as above: I guess nvogvl64.dll is checking texture unit&sample not in use?

ps. Also I checked every shadow sampler in our shaders to ensure correct usage :(

Is there any way to fix these warnings?

2

I finally resolved this: the driver’s warning is right because Angle has a special feature called alwaysCallUseProgramAfterLink.
So glUseProgram is called when program get linked automatically, makes GLContext dirty.

After disabling this feature, warning goes as expected.