Bug 54142

Summary:	Mesa: User error: GL_INVALID_OPERATION
Product:	Mesa	Reporter:	Alexandre Demers <alexandre.f.demers>
Component:	Mesa core	Assignee:	mesa-dev
Status:	RESOLVED NOTOURBUG	QA Contact:
Severity:	normal
Priority:	medium
Version:	git
Hardware:	Other
OS:	All
Whiteboard:
i915 platform:		i915 features:
Attachments:	The culprit shader

Description Alexandre Demers 2012-08-28 06:01:24 UTC

Download and compile GL3_parallax_DoF from http://www.autistici.org/encelo/prog_gldemos.php

Nothing is displayed in the demo and the following error message is thrown in the terminal:
Mesa: User error: GL_INVALID_OPERATION in glUseProgram(program 1 not linked)
Mesa: User error: GL_INVALID_OPERATION in glGetUniformLocation(program not linked)


With mesa git f9767dac9a06aad93a9d61d108055ad673498bf8
drm git 7080bfdfd9b6c5f003daaef37ae9c329f2d46a6c
kernel 3.6.0-rc2

Using HD6950

Comment 1 Laurent carlier 2012-08-28 06:33:53 UTC

Created attachment 66199 [details]
The culprit shader

Comment 2 Laurent carlier 2012-08-28 06:34:54 UTC

When adding more verbosity:

Loading shaders/first.frag
0:45(11): error: assignment to read-only variable 'lightDir'
error: linking with uncompiled shaderLoading shaders/second.vert

Comment 3 Laurent carlier 2012-08-28 07:20:53 UTC

"A varying variable must be written on a vertex shader, where we compute the value of the variable for each vertex. In the fragment shader the variable, whose value results from an interpolation of the vertex values computed previously, can only be read."

lightDir is a varying that was write in the vertex shader, so it can only be read in the fragment shader

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