BOOL to bool

I faced a very simple problem the other day. The compiler started generating a warning:

warning C4800: 'int' : forcing value to bool 'true' or 'false' (performance warning)

The reason being that because I was including some Windows file that included windef.h. In windef.h, it says: typedef int BOOL;

What I was trying to do was to cast that BOOL to bool. Of course we can suppress the warning easily by the #pragma directives as discussed earlier but there has to be a better and a simpler way. Then it clicked, how about a simple != 0 comparison. Here is the sample code:

//Program tested on Microsoft Visual Studio 2008 - Zahid Ghadialy
#include<iostream>
#include<windows.h>
#include<windef.h>

using namespace std;

int main()
{
  BOOL someVal = 1;

  bool firstApproach = someVal; //Generates warning C4800
  cout<<"firstApproach = "<<firstApproach<<endl;

  bool secondApproach = (someVal != 0); //No Warning
  cout<<"secondApproach = "<<secondApproach<<endl;

  return 0;
}

Suppress Compiler Warning using #pragma

Ocassionally the compiler can throw out warnings which may be informative to you but you do not want others to see. You can use a #pragma directive to suppress the warnings. An example of the code below:

//Program tested on Microsoft Visual Studio 2008 - Zahid Ghadialy

//This example shows how to suppress warnings using #pragma

#include<iostream>



using namespace std;



class error

{

public:

  error(string s)

  {

    info = s;

  }

private:

  error();

  string info;

};



#pragma warning( disable : 4290 )



int someFunc(void) throw (error)

{

  return 1;

}



#pragma warning( default : 4290 )



int someOtherFunc(void) throw (error)

{

  return 1;

}



int main()

{



  return 0;

}

Here, for 'someOtherFunc', the compiler will generate a warning:

warning C4290: C++ exception specification ignored except to indicate a function is not __declspec(nothrow)

but a similar warning for 'someFunc' wont be generated because we have already suppressed it using the #pragma.