问尝试解决C语言中一个未知的分段错误

EN

#include <stdio.h>
#include <math.h>
#define SWAP(a,b) tempr=(a);(a)=(b);(b)=tempr

void four1(float data[], unsigned long nn, int isign)
{
        unsigned long n,mmax,m,j,istep,i;
        double wtemp,wr,wpr,wpi,wi,theta;
        float tempr,tempi;

        n=nn << 1;
        j=1;
        for (i=1;i<n;i+=2) {
                if (j > i) {
                        SWAP(data[j],data[i]);
                        SWAP(data[j+1],data[i+1]);
                }
                m=n >> 1;
                while (m >= 2 && j > m) {
                        j -= m;
                        m >>= 1;
                }
                j += m;
        }
        mmax=2;
        while (n > mmax) {
                istep=mmax << 1;
                theta=isign*(6.28318530717959/mmax);
                wtemp=sin(0.5*theta);
                wpr = -2.0*wtemp*wtemp;
                wpi=sin(theta);
                wr=1.0;
                wi=0.0;
                for (m=1;m<mmax;m+=2) {
                        for (i=m;i<=n;i+=istep) {
                                j=i+mmax;
                                tempr=wr*data[j]-wi*data[j+1];
                                tempi=wr*data[j+1]+wi*data[j];
                                data[j]=data[i]-tempr;
                                data[j+1]=data[i+1]-tempi;
                                data[i] += tempr;
                                data[i+1] += tempi;
                        }
                        wr=(wtemp=wr)*wpr-wi*wpi+wr;
                        wi=wi*wpr+wtemp*wpi+wi;
                }
                mmax=istep;
        }
}

void fourier_transform_test (FILE* output_file)
{
        /* 
        This function serves as a test to see whether my implementation of the
        fft is working or not.
        */
        int n = 30;             // number of samples
        float x[n];             // array that holds all values for x            

        // misc
        int i = 0;

        printf("Running fourier transform tests...\n");
        fprintf(output_file, "# x t\n"); 

        // fill the array x with values to be transformed
        for (i = 0; i <= (n - 1); i++) 
                x[i] = cos((2 * 3.1415 * i) / 10);

        // according to the Numerical Recipies, I have to decrement the pointer to data
        // by one to compensate for the zero-offset
        four1(x-1, 64, 1);

        // loop through the transformed array x and print results to a file
        for (i = 0; i <= (n - 1); i++)
                fprintf(output_file, "%i\t%f\n", i, x[i]);

        fclose(output_file);

}

int main (int argc, char *argv[]) 
{
        // open data_file to write results
        FILE* file; 
        if (argc == 1)
                file = fopen("results.dat", "w");
        else
                file = fopen(argv[1], "w");

        fourier_transform_test(file);

        return 0;
}