Assigning const char* to char*

Question

#include <cstring>

char* str0;
const char* str1 = "abc";


// assign str1 to str0
strcpy(str0, str1);    // syntax correct, but run time error
str0 = str1;           // syntax error, cannot convert const char* to char*
string n_str = str1;
str0 = n_str;          // syntax error, cannot convert ...


cout << str0 << endl;  // expected output: abc

I'd like to make str0 same as str1 while runtime(after compilation), I don't know how to do it. And for the case str0 = str1; I don't understand why it won't work, because str0 points to nothing, while str1 points to a const string literal, so if I now make str0 point to what str1 is pointing to, it should be fine, but it is not. So it there any way to solve it?

Answer 1

std::string str0;
const std::string str1 = "abc";

// assign str1 to str0
str0 = str1;

cout << str0 << endl;  // output: abc

If you insist on using C:

char* str0;
const char* str1 = "abc";

str0 = malloc(strlen(str1) + 1);
// if you use a c++ compiler you need instead:
// str0 = (char*) malloc(strlen(str1) + 1);

strcpy(str0, str1);

// and free after use
// if you use C++ this will not help much
// as pretty much any exception above will cause your code to get out of `free`,
// causing a memory leak
free(str0);

If you insist on using bad C++:

char* str0;
const char* str1 = "abc";

str0 = new char[strlen(str1) + 1];

strcpy(str0, str1);

// and delete after use
// this will not help much
// as pretty much any exception above will cause your code to get out of `delete`,
// causing a memory leak
delete(str0);

Please read about RAII to understand why all of the solutions with manual memory management are bad: cppreference , wiki