CODEWITHSUNDEEP
carrayscompiler-errorssize
Alroc
Alroc

Reputation: 117

Error C2057 expected constant expression while using a constant

Here is my problem, I must be missing something here.

 const int nfft = 256 * 1024;
const float samplefrequency = 256.0 * 1024.0 ; // Hz

/* The buffer, spectral and data arrays for the FFT */
kiss_fft_cfg mybuff;
kiss_fft_cpx samples[nfft];
kiss_fft_cpx fftoutput[nfft];

/* The final, averaged spectrum */
double finalspec[nfft/2];

So this is a part of my code.

The problem is that i can't compile it because of : "error C2057: expression constante attendue" line 16 - kiss_fft_cpx samples[nfft]; "error C2057: constant expression required"

I don't understand what is wrong considering the fact that nfft is a constant.

Thanks

Upvotes: 1

Views: 2809

Answers (1)

cnicutar
cnicutar

Reputation: 182684

I don't understand what is wrong considering the fact that nfft is a constant

In C const variables aren't really constants, more like read-only objects. As such, they can't be used in all the places where true constants could be used (for example the size of an array).

Perhaps you could use a macro instead:

#define NFFS (256 * 1024)

Incidentally there's also a C FAQ entry on this subject: I don't understand why I can't use const values in initializers and array dimensions.

Upvotes: 2

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