C / C++ / MFC

«_Superman_» wrote:

First, you cannot use extern "C" if you're using std::string

«_Superman_» wrote:

My mistake.

return "some value";

char* str; or std::string str;

return str; 

String str = somefunctionname(); 

// yourfile.h
extern "C" std::size_t requiredSize();
extern "C" std::size_t getString(char* buffer);

// yourfile.cpp
char mystring[] = "hello world";     // just an example
std::size_t requiredSize() {
   return sizeof(mystring) / sizeof(char);  // an upper limit to the size required for getString
}
std::size_t getString(char* buffer) {
   if (!buffer)                      // error: no buffer provided!
       return 0;                     // response: 0 bytes copied
   strcpy(buffer, mystring);         // hope for the best and just copy
   return requiredSize();            // return the length of the copied string
}

#include "yourfile.h"
void foo() {
   std::size_t sz = requiredSize();  // inquire required size
   char* mybuffer = new char[sz];    // allocate a sufficiently large buffer
   getString(buffer);                // get the string
   puts(buffer);                     // do something with the string (in this case, print it)
   delete [] buffer;                 // release the buffer
}

#include <stdio.h >


char *return_Char_Pointer(char *ptrChar)
{
	ptrChar = "hello hi! I am returning a return char pointer (char *p)\n\n";
	return ptrChar;
}


int main(int argc, char* argv[])
{
	char *ptrChar = new char[255];
	char *ptrChar1;
	ptrChar1 =return_Char_Pointer(ptrChar);

	printf("%s",ptrChar1);
	delete []ptrChar;
	
	return 0;
}

Stefan_Lang wrote:

The caller may not know what method was used to allocate the memory (e. g.
malloc or new), or if it was allocated at all, or instead just points to a
static buffer!

Stefan_Lang wrote:

The OP put this function into a library interface