in h3_vertex.c [297:312]
H3Error H3_EXPORT(cellToVertexes)(H3Index cell, H3Index *vertexes) {
// Get all vertexes. If the cell is a pentagon, will fill the final slot
// with H3_NULL.
bool isPent = H3_EXPORT(isPentagon)(cell);
for (int i = 0; i < NUM_HEX_VERTS; i++) {
if (i == 5 && isPent) {
vertexes[i] = H3_NULL;
} else {
H3Error cellError = H3_EXPORT(cellToVertex)(cell, i, &vertexes[i]);
if (cellError) {
return cellError;
}
}
}
return E_SUCCESS;
}