A piece of code

Look at following code:

#include <stdio.h>

int main()
{
    char *s = "hello world";
    puts(s);
}

Note that puts is basically a printf like funtion but without format functinalities.

Now using the following command to compile as a c program.

gcc puts_test.c -o puts_test_c

There are no errors emitted.

However if we compile as C++ program:

g++ -std=c++14 -o puts_test puts_test.cpp
puts_test.cpp:5:15: warning: ISO C++11 does not allow conversion from string literal to 'char *' [-Wwritable-strings]
    char *s = "hello world";
              ^
1 warning generated.

It complains.

This is just an simple example how C++ improves the type safe: char *s is mutable, however a string literal is not: we could not simple assign a literal to a mutable variable.

How to fix

Using const char * instead of char *.

a bit more

To make the C++ program more with C++ style:

#include <cstdio>

int main()
{
    const char *s = "hello world";
    std::puts(s);
}