Why does the compiler prefer f(const void*) to f(const std::string &)?

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Consider the following piece of code:

#include <iostream> #include <string>  // void f(const char *) { std::cout << "const char *"; } // <-- comment on purpose void f(const std::string &) { std::cout << "const std::string &"; } void f(const void *) { std::cout << "const void *"; }  int main() {     f("hello");     std::cout << std::endl; } 

I compiled this program using g++ (Ubuntu 6.5.0-1ubuntu1~16.04) 6.5.0 20181026:

$ g++ -std=c++11 strings_1.cpp -Wall $ ./a.out  const void * 

Note that the comment is there on purpose to test, otherwise the compiler uses f(const char *).

So, why does the compiler pick f(const void*) over f(const std::string &)?

 


Converting to a std::string requires a "user defined conversion".

Converting to void const* does not.

User defined conversions are ordered behind built in ones.

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