Shader linking fails when editing a copy of gl_PointCoord

[namespace]

Hi!

I try to fake rotatable pointsprites by rotating the calculated
gl_PointCoord in the fragment shader.
For some strange reason the linking of the program
fails as soon as I try to modify a _copy_ of the gl_PointCoord
values.
This is the error (including a typo from a nv dev ):
error C7001: inconsitent use of semantic modifiers: "sin_a" and "gl_PointCoord"

This is my fragment shader:

uniform sampler2D u_base;
 
varying float sin_a;
varying float cos_a;
 
void main()
{
	// apply rotation
	vec2 coords = gl_PointCoord;
	/*
	coords = coords * 2.0 - 1.0; // [0, 1] ->[-1, 1]
	float xx = cos_a * coords.x + sin_a * coords.y;
	coords.y = -sin_a * coords.x + cos_a * coords.y;
	coords.x = xx;
	coords = (coords + 1.0) * 0.5;  // [-1, 1] -> [0, 1]
	*/
 
	vec3 color = texture2D(u_base, coords).rgb;
	gl_FragColor = vec4(color, 1.0) * gl_Color;
}

The vertex shader

 varying float sin_a;
 varying float cos_a;
 
 void main()
 {
 	vec4 vtx = gl_ModelViewMatrix * vec4(gl_Vertex.xyz, 1.0);
 
 	// distance attenuation
	// add an epsilon 'cause zero size is undefined for pointsprites
	gl_PointSize = VIEWPORT_WIDTH * gl_Vertex.w * 2.0 / -vtx.z + 0.01;
 
	// decode color and rotation
	vec4 tmp = gl_MultiTexCoord0;
	gl_FrontColor = vec4(tmp.r, tmp.g, fract(tmp.b) * 10.0, fract(tmp.a) * 10.0);
 
	sin_a = tmp.b / 1000000.0;
	cos_a = tmp.a / 1000000.0;
 
	gl_Position = gl_ProjectionMatrix * vtx;
 }

As soon as I remove the comments around the
codeblock that recalculates the coords, the linking fails.

Card used: Geforce 8 GTS
Version: 2.1.1 NVIDIA 100.14.19
OS is Linux

[Trenki]

Just guessing: gl_PointCoord is olny available in GLSL 1.20. Maybe you should put a #version 120 at the top of your fragment shader source?

[ www.trenki.net | vector_math (3d math library) | software renderer ]

[namespace]

I do that.
What I have posted is the raw shader-source,
my engine adds a set of preprocessor macros
and defines at the top of each shaderfile, with
"#version 120" beeing one of them.

[namespace]

Anybody?

[Y-tension]

Is it the linking or the compilation that fails?

[yooyo]

I just tested in Shader Designer on WinXP-SP2 + 7600GT fw 163.69 and it works.

[namespace]

Is it the linking or the compilation that fails?

Linking fails.

Originally posted by yooyo:
I just tested in Shader Designer on WinXP-SP2 + 7600GT fw 163.69 and it works.

That is good news, I guess I have to wait for a Linux driverupdate then.