The BasicCallGraph class only lines out the indirect calls(makes the caller
point to external node),
but do not resolves them using alias analysis such as DSA.
I think DSA solve this problem for interested call sites by finding the
corresponding globals(i.e. the functions)
for the callsite DSnode.
Yes, if we want to determine all indirect call(including function pointers in
structs, arrays), we should improve DSA to analyze function pointer, and then
exploit pointing set of function pointer in callgraph analysis.