CODEWITHSUNDEEP
c++cross-platformc-preprocessor
bahrami703i
bahrami703i

Reputation: 33

Cross Platform programming on C++

I want to make a program work and compile in both WIN\Linux .
I want to have some information about the OS which my program is ran on.
moreover I want to have a variable to decide about the code i want to be performed.

I thought about a pre-processed code to have an input to my controlling variable which I described.
So, I must have something like:

#  //a preprocess code to detect the os
# define controllingVar // ?

I use C++;

Upvotes: 1

Views: 251

Answers (2)

Attila
Attila

Reputation: 28762

You can deduce what platform your code is being compiled for by using (compiler specific) pre-processor macros, like WIN32 and the like. There is no easy way to deduce what platform your program is running on (other than it is most likely running on a platform it was compiled for) -- you will need to perform platform/OS specific calls for that.

You could do something like this:

#ifdef WIN32 // compiler specific, WIN32 is defined in Visual Studio
  // Windows specific code
  // include Windows specific headers
  int controllingVar = 0; // 0 - Windows
#else
  // For everything else
  // Here: assume Unix/Linux
  // include Linux specific headers
  int controllingVar = 1; // 1 - non-Windows
#endif

After this you can refer to controllingVar in your code. controllingVar will have the value 0 if the program was compiled for Windows, 1 otherwise (and you can go with the assumption of Linux).

The #ifdef part enables conditional compilation -- the code within the Windows specific block is compiled only when compiled for Windows, the other in any other case.

Note that this essentially requires a duplication of coding, maintenance and testing efforts, so try to put only the most essential code in the conditional blocks and anything that is not platform specific outside it.

Upvotes: 1

mfontanini
mfontanini

Reputation: 21900

You could check if the WIN32 macro has been defined:

#ifdef WIN32
   // do windows stuff
#else
   // do GNU/Linux stuff
#endif

Note that on some compilers, you might also have to check for _WIN32, as stated in wikipedia.

As an example:

#ifdef WIN32
   void foo() {
       std::cout << "I'm on Windows!\n";
   }
#else
   void foo() {
       std::cout << "I'm on GNU/Linux!\n";
   }
#endif

Edit: since you're asking about different mains for each OS, here's an example:

int main() {
#ifdef WIN32
   // do whatever you want when executing in a Windows OS
#else
   // do the same for GNU/Linux OS.
#endif
}

You could also have different mains:

#ifdef WIN32
   int main() {
       //windows main
   } 
#else
   int main() {
       //GNU/Linux main
   } 
#endif

Upvotes: 3

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