c++ - string to char* conversion -

i in code base there lots of function calls functions take pointer argument. however, function call passes "string" object if it's pointer. following code shown give idea.

#include <vector> #include <unordered_map> #include <iostream> #include <stdlib.h> #include <string.h> #include <string>  using namespace std;  void dum(char *s) {     printf("%s\n", s); }  operator char* (string s) {     return s.c_str(); }  int main(int argc,char *argv[]) {     string st("hello world");     dum(st);     return 0; } 

i not allowed change syntax these functions or function calls. 1 possible solution came add operator overload, unfortunately doesn't work, here error g++ (ver 4.7.3), command line: g++ -std=c++11 te2.cc

error: ‘operator char*(std::string)’ must nonstatic member function 

any ideas? thanks.

update1

@ferruccio's answer reminded me mention there function calls like

dum(dum2()); 

where dum2() function like:

string dum2() {     string s;     //.....     return s; } 

so wrapper following doesn't work (), compiler gives error no matching function call ‘dum(std::string)’

void dum(string &s) {     dum(s.c_str()); } 

you add simple function overload each function takes char*. e.g.

void dum(const string& s) {     dum(s.c_str()); }