[Mesa-dev] [PATCH 01/11] mesa: Returns a GL_INVALID_VALUE error on several glGet* APIs when max length is negative

[Ian Romanick]

On 01/19/2015 04:35 AM, Erik Faye-Lund wrote:
> On Mon, Jan 19, 2015 at 1:31 PM, Erik Faye-Lund <kusmabite at gmail.com> wrote:
>> On Mon, Jan 19, 2015 at 12:32 PM, Eduardo Lima Mitev <elima at igalia.com> wrote:
>>> The manual page for glGetAttachedShaders, glGetShaderSource, glGetActiveUniform and
>>> glGetActiveUniform state that a GL_INVALID_VALUE is returned if the maximum length
>>> argument is less than zero. For reference, see:
>>> https://www.opengl.org/sdk/docs/man3/xhtml/glGetAttachedShaders.xml,
>>> https://www.khronos.org/opengles/sdk/docs/man31/html/glGetAttachedShaders.xhtml,
>>> https://www.opengl.org/sdk/docs/man3/xhtml/glGetShaderSource.xml,
>>> https://www.khronos.org/opengles/sdk/docs/man31/html/glGetShaderSource.xhtml,
>>> https://www.opengl.org/sdk/docs/man3/xhtml/glGetActiveUniform.xml,
>>> https://www.khronos.org/opengles/sdk/docs/man31/html/glGetActiveUniform.xhtml,
>>> https://www.opengl.org/sdk/docs/man3/xhtml/glGetActiveAttrib.xml,
>>> https://www.khronos.org/opengles/sdk/docs/man31/html/glGetActiveAttrib.xhtml.
>>>
>>> This fixes 4 dEQP test:
>>> * dEQP-GLES3.functional.negative_api.state.get_attached_shaders
>>> * dEQP-GLES3.functional.negative_api.state.get_shader_source
>>> * dEQP-GLES3.functional.negative_api.state.get_active_uniform
>>> * dEQP-GLES3.functional.negative_api.state.get_active_attrib
>>
>> These tests are about GLES3, but I cannot find such behavior specified
>> in the OpenGL ES 3.0 specification for GetAttachedShaders nor
>> GetProgramBinary. I stopped checking after those two, because I felt I
>> saw a pattern ;)
>>
>> The man pages you linked to are for desktop-OpenGL, which *does*
>> specify such an error; OpenGL 4.5 spec says "An INVALID_VALUE error is
>> generated if maxCount is negative" about GetAttachedShaders (and a
>> similar for GetProgramBinary()).
>>
>> However, the GLES 3 man pages also list such an error:
>> https://www.khronos.org/opengles/sdk/docs/man3/html/glGetAttachedShaders.xhtml
>>
>> Generally speaking, the manual pages are not considered to dictate
>> behavior, only to be a programmer convenience. And they have
>> historically been full of errors. However, since desktop GL *does*
>> specify these errors *and* the man-pages document them, this does look
>> like a spec-error for GLES 3 to me. But I think we should get a
>> clarification from Khronos before assuming so, otherwise we won't be
>> in conformance. Ian, any thoughts?
> 
> By the way, this error is also properly defined for OpenGL ES 3.1, so
> I'm feeling even more confident that it's a spec-bug in OpenGL ES 3.0.

There's a general statement in the Errors section that passing a
negative value for a GLsizei or GLsizeiptr is always an INVALID_VALUE
error.  That exists in all specs back to OpenGL 1.0. :)  Since it's in a
different place, it is often overlooked (like when we wrote these
functions in Mesa).