一个简单的cudaMemcpy，大神看看哪错了

[baidu_28806005]

int main()
{
if (!InitCUDA()) return 0;
int *a;
int *d_a ;
int *h_a;
int b = 8;
a = &b;
printf("a is %d\n",*a);
cudaError_t error;
h_a = (int *)malloc(sizeof(int));
a = (int *)malloc(sizeof(int));
error = cudaMalloc((int **)&d_a,sizeof(int));
if (error != cudaSuccess)
error = cudaMemcpy(d_a,a,sizeof(int),cudaMemcpyHostToDevice);
cudaDeviceSynchronize();
if (error != cudaSuccess)
{
printf("cudaMemcpy returned error %s (code %d), line(%d)\n", cudaGetErrorString(error), error, __LINE__);
exit(EXIT_FAILURE);
}
else
printf("success");
error = cudaMemcpy(h_a,d_a,sizeof(int),cudaMemcpyDeviceToHost);
cudaDeviceSynchronize();
printf("cuda is %d\n",*h_a);
free(a);
free(h_a);
cudaFree(d_a);

}