Question

In my OpenCL code (which is not coded by myself, it’s just an example code from internet), there is the following sentence to use the function of clamp.

return clamp(color,0,1);

However it seems that this makes error during compilation, so I got the error info message by using CL_PROGRAM_BUILD_LOG from clGetProgramBuildInfo.

Error during compilation! (-11)
4483
build log
:211:9: error: call to 'clamp' is ambiguous
        return clamp(color,0,1);
               ^~~~~
<built-in>:3558:26: note: candidate function
float4  __OVERLOADABLE__ clamp(float4 x, float min, float max)   ;
                         ^
<built-in>:3577:25: note: candidate function
float4 __OVERLOADABLE__ clamp(float4, float4, float4);
                        ^
<built-in>:3556:26: note: candidate function
float3  __OVERLOADABLE__ clamp(float3 x, float min, float max)   ;
                         ^
<built-in>:3575:25: note: candidate function
float3 __OVERLOADABLE__ clamp(float3, float3, float3);
                        ^
:296:52: error: address expression must be an lvalue or a function designator
                                r.origin = matrixVectorMultiply(viewTransform, &(float3)(0, 0, -1));
                                                                               ^~~~~~~~~~~~~~~~~~
:297:62: error: address expression must be an lvalue or a function designator
                                r.dir    = normalize(matrixVectorMultiply(viewTransform, &(float3)(x, y, 0)) - r.origin);
                                                                                         ^~~~~~~~~~~~~~~~~

Is there any necessary keyword for using clamp function in OpenCL code? BTW, I’m using the environment of the Linux Ubuntu 10.04 64bit.

Answer 1

Try the following

return clamp(color,0.0f,1.0f);

This way we know for sure that 2nd and 3rd params are not ambiguous and that you are trying to call the function:

clamp(float4 color, float min, float max);

If this doesn’t work, then see your color param, but the 2nd and 3rd param should be fine now.