I have this shader that works well on my computer (using an ATI HD 5700). I have a loop iterating between two constant values, which is, afaik, acceptable in a glsl shader. I write stuff in two arrays in this loop.

#define NB_POINT_LIGHT 2

...

varying vec3 vVertToLight[NB_POINT_LIGHT];
varying vec3 vVertToLightWS[NB_POINT_LIGHT];

...

void main()
{
    ...
    for (int i = 0; i < NB_POINT_LIGHT; ++i)
    {
        if (bPointLightUse[i])
        {
            vVertToLight[i] = ConvertToTangentSpace(ShPointLightData[i].Position - WorldPos.xyz);
            vVertToLightWS[i] = ShPointLightData[i].Position - WorldPos.xyz;
        }
    }
    ...
}

I tried my program on another computer equipped with an nVidia GTX 560 Ti, and it fails to compile my shader. I get the following errors (94 and 95 are the lines of the two affectations) when calling glLinkProgram:

Vertex info
-----------
0(94) : error C5025: lvalue in assignment too complex
0(95) : error C5025: lvalue in assignment too complex

I think my code is valid, I don't know if this comes from a compiler bug, a conversion of my shader to another format from the compiler (nvidia looks to convert it to CG), or if I just missed something.

I already tried to remove the if (bPointLightUse[i]) statement and I still have the same error. However, if I just write this:

vVertToLight[0] = ConvertToTangentSpace(ShPointLightData[0].Position - WorldPos.xyz);
vVertToLightWS[0] = ShPointLightData[0].Position - WorldPos.xyz;
vVertToLight[1] = ConvertToTangentSpace(ShPointLightData[1].Position - WorldPos.xyz);
vVertToLightWS[1] = ShPointLightData[1].Position - WorldPos.xyz;

Then I don't have the error anymore, but it's really unconvenient so I would prefer to keep something loop-based.

Here is the more detailled config that works:

Vendor: ATI Technologies Inc.
Renderer: ATI Radeon HD 5700 Series
Version: 4.1.10750 Compatibility Profile Context
Shading Language version: 4.10

And here is the more detailed config that doesn't work (should also be compatibility profile, although not indicated):

Vendor: NVIDIA Corporation
Renderer: GeForce GTX 560 Ti/PCI/SSE2
Version: 4.1.0
Shading Language version: 4.10 NVIDIA via Cg compiler