Basic Pointers - Basic Pointers - 2026.1 English - UG1399

A function with basic pointers on the top-level interface, such as shown in the following code example, produces no issues for Vitis HLS. The pointer can be synthesized to either a simple wire interface or an interface protocol using handshakes.

#include "pointer_basic.h"
void pointer_basic (dio_t *d) {
static dio_t acc = 0;
acc += *d;
*d  = acc;
}

The pointer on the interface is read or written only once per function call. The test bench is shown in the following code example.

#include "pointer_basic.h"
int main () {
dio_t d;
int i, retval=0;
FILE *fp;
// Save the results to a file
fp=fopen(result.dat,w);
printf( Din Dout\n, i, d);
// Create input data
// Call the function to operate on the data
for (i=0;i<4;i++) {
    d = i;
    pointer_basic(&d);
    fprintf(fp, %d \n, d);
    printf(  %d   %d\n, i, d);
}
fclose(fp);
// Compare the results file with the golden results
retval = system(diff --brief -w result.dat result.golden.dat);
if (retval != 0) {
    printf(Test failed!!!\n);
    retval=1;
} else {
    printf(Test passed!\n);
}
// Return 0 if the test
return retval;
}

C and RTL simulation verify the correct operation (although not all possible cases) with this simple data set:

Din Dout
  0   0
  1   1
  2   3
  3   6
Test passed!