Initialize global variable in c++

Question

I declared a Boolean global variable in the ".h" file, and initialize it the ".cpp" file, I faced an error, i searched on the solution and found that i must define it as extern as following:

//in .h file
extern bool blindFound;

// in .cpp file
bool blindFound = false;

But when i print its value inside other methods, it gave me ( Null ) not false!!

Thanks,

Answer 1

printf(" blindFound: %s \n", blindFound ); 

Is it C or C++ ? Also your compiler should have warned you. Turn the warning on and pay attention to them.

Now the error is that you are printing a boolean as a string "%s". You should print it as a integer "%d". Then false will appear as 0 and true as 1.

Answer 2

You should use std::boolapha is C++.

The answer Above is a little mistake.

http://www.parashift.com/c++-faq-lite/iostream-vs-stdio.html

Please try to avoid old printf from C.

http://www.cplusplus.com/reference/ios/boolalpha/

// modify boolalpha flag
#include <iostream>     // std::cout, std::boolalpha, std::noboolalpha

int main () {
  bool b = true;
  std::cout << std::boolalpha << b << '\n';
  std::cout << std::noboolalpha << b << '\n';
  return 0;
}

Answer 3

It is often better to wrap such variables in functions, making them local static objects. This effectively avoids order-of-initialization issues.

bool &blindFound()
{
  static bool blindFound = false;
  return blindFound;
}

Usage:

blindFound() = true; // set value
bool b = blindFound(); // read value

Have a look at the C++ FAQ for more information about the so-called "static initialization order fiasco".