为什么我的fprintf无法将stdout作为流传递？

I have the following function:

我有以下功能:

void print_out_str(FILE* outstream, UINT x, int n) {

   assert(n >= 1);

   int n1, n2, j;

   n1 = (n - 1)/64; n2 = n % 64;
   for(j = 0; j <= n1 - 1; j++) 
      fprintf(outstream,"%016llx ",x[j]); //padding with 0
   fprintf(outstream,"%016llx ",x[n1] & ((1ULL<<n2) - 1ULL));
void