CODEWITHSUNDEEP
c++c-preprocessor
Colen
Colen

Reputation: 13908

C++ preprocessor directive limits

I have a C++ pre-processor directive that is something like this:

#if (SOME_NUMBER != 999999999999999)
// do stuff
#endif

999999999999999 is obviously greater than 232, so the value won't fit into a 32-bit integer. Will the preprocessor correctly use a 64-bit integer to resolve the comparison, or will it truncate one or both of the values?

Upvotes: 4

Views: 629

Answers (3)

David Thornley
David Thornley

Reputation: 57046

Preprocessor arithmetic works as normal constant expressions (see the Standard, 16.1/4), except that int and unsigned int are treated as if they were long and unsigned long. Therefore, if you have a 64-bit type, you can use it as normal.

Upvotes: 1

kikito
kikito

Reputation: 52668

You can try using the UINT_MAX constant defined in "limits.h":

#if (SOME_NUMBER != UINT_MAX)
// do stuff
#endif

UINT_MAX value varies depending on the integer size.

Upvotes: 1

Murilo Vasconcelos
Murilo Vasconcelos

Reputation: 4827

Try to use the LL suffix:

#if (SOME_NUMBER != 999999999999999LL)
// do stuff
#endif

In my gcc this work fine:

#include <iostream>

#define SOME_NUMBER 999999999999999LL

int main()
{

#if (SOME_NUMBER != 999999999999999LL)
    std::cout << "yes\n";
#endif

    return 0;
}

With or without the LL suffix.

Upvotes: 2

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