nm foo | grep malloc
         U malloc@@GLIBC_2.2.5

find_usages foo-with-debug-symbols "malloc@@GLIBC_2.2.5"

#include <string>

int main() {
  auto s = std::string("hello");
  s += " welt";
  return 0;
}

g++ foo.cpp -static

r2 -qAc 'agCd' a.out > callgraph.dot