Hi,
Recently, I've been working on scripts for a GLSL fuzz testing framework that
use piglit's shader_runner to render shaders. As part of the test generation
process, shaders can be generated that declare uniforms without using them
(which is valid GLSL according to glslangvalidator). One of my scripts turns
the shader and uniform data from the framework's test format into a shader_test
file and runs it via shader_runner_gles3.
However, it seems that some of these unused uniforms are optimized away when
the shader is compiled, and when shader_runner tries to use the uniform data in
the [test] header, it can't find the location of the given uniform and throws
an error.
Relevant code (there are similar pieces of code in the file for vertex and
subuniforms):
piglit/tests/shaders/shader_runner.c, line 2289:
> loc = glGetUniformLocation(prog, name);
> if (loc < 0) {
> printf("cannot get location of uniform \"%s\"\n",
> name);
> piglit_report_result(PIGLIT_FAIL);
> }
I'd like to discuss whether it'd be possible to instead just ignore a piece of
uniform data if the corresponding uniform can't be found in the compiled shader
(I'd be willing to submit a patch for this).
Something like:
> loc = glGetUniformLocation(prog, name);
> if (loc < 0) {
> printf("cannot get location of uniform \"%s\"\n",
> name);
> return;
> }
>From my limited grepping of the code, there doesn't seem to be anything that
>would fail horribly if this were to be changed (as the setting of a uniform
>only occurs at the end of set_uniform, after various checks like this), but
>please correct me if I'm wrong about any of this.
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