deprecated conversion from string constant to 'char*' [duplicate]

Answer 1

I want to pass a string via char* to a function.

Here is how you can pass a string via char* to a function (note the required const keyword in the function signature.)

#include 
void f(const char* p) {
  std::cout << p << "\n";
}

int main() {
  f("Access");
}

But, what if you are invoking an existing function, and cannot modify its signature?

If you have some external guarantee that the function will not write through its argument pointer,

#include 
void f(char* p) {
  std::cout << p << "\n";
}

int main() {
  f(const_cast("Access"));
}

If, on the other hand, the function might write to the string, then you'll need to allocate space for the string:

#include 
void f(char* p) {
  *++p;
  std::cout << p << "\n";
}

int main() {
  // Allocate read-write space on the heap
  char *p = new char[strlen("Access"+1)];
  // Copy string to allocated space
  strcpy(p, "Access");
  f(p);
  delete p;
}

or,

#include 
void f(char* p) {
  *++p;
  std::cout << p << "\n";
}

int main() {
  // Allocate read-write space on the stack
  char arr[] = "Access";
  f(arr);
}

But, the best course by far is to avoid the whole pointer mishegas:

#include 
void f(const std::string& p) {
  std::cout << p << "\n";
}

int main() {
  f("Access");
}