cudaMemcpyToSymbol using or not using string

Question

I was trying to copy a structure to constant memory in this way:

struct Foo {
    int a, b, c;
};

__constant__ Foo cData;

int main() {
    Foo hData = {1,          


        

Answer 1

Because of getting the same error again and again, I want to share this sample code that shows nearly all of the example cases for this problem (so I may refer here later when I make same mistakes again).

//file: main.cu
#include 
#include 
#include 

__constant__ float constData[256];
__device__ float devData;
__device__ float* devPointer;

int main(int argc, char **argv)
{
  cudaFree(0);

  float data[256];
  cudaError_t err = cudaMemcpyToSymbol(constData, data, sizeof(data));
  printf("Err id: %d, str: %s\n", err, cudaGetErrorString(err));

  float value = 3.14f;
  err = cudaMemcpyToSymbol(devData, &value, sizeof(float));
  printf("Err id: %d, str: %s\n", err, cudaGetErrorString(err));

  float* ptr;
  cudaMalloc(&ptr, 256 * sizeof(float));
  err = cudaMemcpyToSymbol(devPointer, &ptr, sizeof(ptr));
  printf("Err id: %d, str: %s\n", err, cudaGetErrorString(err));
  cudaFree(ptr);

  return EXIT_SUCCESS;
}

I was getting "invalid device symbol" and many others which are related to _constant_ _device_ memory usage. This code gives no such errors at runtime.