Thread: error: expression must have pointer-to-object type

I have been working on a code using FFTW3 and i have gotten the program down to giving only one error: " error: expression must have pointer-to-object type" but multiple times.

The parts giving me trouble are the pointers for fftw_complex, here is everywhere these pointers (fourier_u,fourier_v, and fourier_w) are referenced in my code:

Code:

fftw_complex *fourier_u,*fourier_v,*fourier_w;
...        
fourier_u = ( fftw_complex* ) fftw_malloc( sizeof( fftw_complex ) *                DIM2 );
fourier_v = ( fftw_complex* ) fftw_malloc( sizeof( fftw_complex ) * DIM2 );
fourier_w = ( fftw_complex* ) fftw_malloc( sizeof( fftw_complex ) * DIM2 );
...
l = 0;
    for(k=0;k<(nz/2)+1;k++)
        for(j=0;j<ny;j++)
            for(i=0;i<nx;i++)
            {
                fur = (double)creal(vt[j][k][0]);
                fui = (double)cimag(vt[j][k][0]);
                fvr = (double)creal(vt[j][k][1]);
                fvi = (double)cimag(vt[j][k][1]);
                fwr = (double)creal(vt[j][k][2]);
                fwi = (double)cimag(vt[j][k][2]);
                                
                fourier_u[l][0] = fur;
                fourier_u[l][1] = fui;
                fourier_v[l][0] = fvr;
                fourier_v[l][1] = fvi;
                fourier_w[l][0] = fwr;
                fourier_w[l][1] = fwi;    
                    l++ 
                     }        
...

I have tested the code and as expected, fur, fui,fvr,fvi,fwr,fwi are all of type double. I tried following an example but when I compile my program (using mpicc) I get the following error message for the last few lines of the portion of the code shown above:

Code:

FinalTurbulence.c(176): error: expression must have pointer-to-object type
                                fourier_u[l][0] = fur;
                                ^

FinalTurbulence.c(177): error: expression must have pointer-to-object type
                                fourier_u[l][1] = fui;
                                ^

FinalTurbulence.c(178): error: expression must have pointer-to-object type
                                fourier_v[l][0] = fvr;
                                ^

FinalTurbulence.c(179): error: expression must have pointer-to-object type
                                fourier_v[l][1] = fvi;
                                ^

FinalTurbulence.c(180): error: expression must have pointer-to-object type
                                fourier_w[l][0] = fwr;
                                ^

FinalTurbulence.c(181): error: expression must have pointer-to-object type
                                fourier_w[l][1] = fwi;
                                ^

I have searched extensively for a solution but have had no luck. Any help would be greatly appreciated. And I can provide more information if needed, but as stated above I included all of the code where the questionable pointers are used. Thanks.

From the FFTW3 manual, in the fftw3.h header fftw_complex is defined as:

Code:

The default FFTW interface uses double precision for all floating-point numbers, and defines a fftw_complex type to hold complex numbers as:


typedef double fftw_complex[2];


Here, the [0] element holds the real part and the [1] element holds the imaginary part.

Also if it helps a working example of a code using the FFTW3 can be found at
FFT with FFTW Example