Question

由于陈述的问题，我对我的程序感到困惑。当我在为数组分配计算值之前或之后放置printf语句时，我得到了正确的答案。否则，这是一个奇怪的数字。这个数字非常一致。 printf不必包含与数组相关的任何内容。我检查了这个answer，但没有得到很多。以下是我的代码的一部分：

int xcorr(Imdata, Kernel, sizeIm, sizeKernel, result_im)
unsigned short** Imdata;
unsigned short** Kernel;
long sizeIm[2], sizeKernel[2];
float** result_im;
{
register float Imstd, Imavg, Kernelstd, Kernelavg, combine_avg, outtmp, area;
register int bufYsize, bufXsize;
    int i,j,r,c;
register unsigned short *ImdataPtr, *KernelPtr;
register float *result;
register float val1, val2;

// kernel average and standard deviation are constant throughout this function
area = sizeKernel[0]*sizeKernel[1];
outtmp = Kernelavg = 0;

// Using the One-pass standard variance algorithm
for(i=0;i<sizeKernel[0];i++){
    KernelPtr = Kernel[i];
       for(j=0;j<sizeKernel[1];j++){
           val1 = KernelPtr[j];
        Kernelavg += val1;
        outtmp += val1*val1;
    }
}
Kernelavg /= area;
outtmp /= area;

// now the standard deviation
Kernelstd = sqrt(outtmp - Kernelavg*Kernelavg);

  /////////////////////////////////////////////////
  // Perform Correlation
  /////////////////////////////////////////////////
  bufYsize = sizeIm[0] - sizeKernel[0] + 1;
  bufXsize = sizeIm[1] - sizeKernel[1] + 1;

for(i=0;i<bufYsize;i++){
    result = result_im[i];
    for(j=0;j<bufXsize;j++){    
        combine_avg = outtmp = Imavg = 0;

        // Using one-pass method for standard variance:
        for (r = 0; r < sizeKernel[0]; r++){
            KernelPtr = Kernel[r];
            ImdataPtr = Imdata[i+r];
            for (c = 0; c < sizeKernel[1]; c++){
                val1 = KernelPtr[c];
                val2 = ImdataPtr[j+c];
                Imavg += val2;
                outtmp += val2*val2;
                combine_avg += val1*val2;
            }
        }
        outtmp /= area;
        Imavg /= area;
        // standard deviation
        if((Imstd = outtmp - Imavg*Imavg)<=SMALL_VAR){
            result[j] = 0;
            continue;
        }
        Imstd = sqrt(outtmp - Imavg*Imavg);

        combine_avg /= area;
        result[j] = (float)combine_avg-(Imavg*Kernelavg))/(Kernelstd*Imstd);

    }
}
return 0;
}

错误与结果有关，该结果在main中分配如下：

result = (float**)malloc(bufYsize*sizeof(float*));
if(result == NULL){
    printf("Error allocating the output array (pair num=%d)\n",k+1);
    xit_status = 1; //exit(EXIT_FAILURE);
    }
else{
for(i=0;i<bufYsize;i++){
    result[i]=malloc(bufXsize*sizeof(float));
       if(result[i]==NULL){ 
       printf("Error allocating the output array at row %d, pair %d\n",i,k+1);
    exit_status = 1; //exit(EXIT_FAILURE);
    }
 }
}

Answer 1

printf应该能够影响变量的唯一方法是通过%n格式说明符。

int x;
printf("foo%nbar\n", &x);
printf("%d\n", x);  // 3

如果正在修改其他任何内容，那么您的程序必须在某处调用未定义的行为。我建议从Valgrind（或类似的）开始追踪它。

什么情况下printf（）会影响c中的变量？

1 个答案: