CODEWITHSUNDEEP
c++c-preprocessor
user245019
user245019

Reputation:

C++ Preprocessor Decisions

Sorry I know this is basic, but perhaps it doesn't exist or I'm not googling the right words. Is there and an if not (is that ifndef?) an AND and an OR so I could do something like:

if not DEBUG and MACOS

Upvotes: 2

Views: 770

Answers (7)

Aoi Karasu
Aoi Karasu

Reputation: 3825

#if, #else and #endif are general. Use #define to declare and #undef to undeclare. Use #ifdef to check if is declared and #ifndef to check, if is not declared.

Example:

#ifndef LABEL
#define LABEL some_value // declares LABEL as some_value
#else
#undef LABEL // undeclare previously declared LABEL...
#define LABEL new_value // to declare a new_value
#endif

Upvotes: 1

Puppy
Puppy

Reputation: 146910

Check out the Boost preprocessing library. It can accomplish a large number of tasks using the preprocessor.

Upvotes: 0

ShadowRanger
ShadowRanger

Reputation: 155323

#if !(defined(DEBUG) && defined(MACOS))

or

#if !defined(DEBUG) && !defined(MACOS)

depending on what you're trying to evaluate.

Upvotes: 1

zerm
zerm

Reputation: 2842

#if !defined(DEBUG) && defined(MACOS)
#error "Ouch!"
#endif

tests, if those macros/values are defined (even set to 0 means defined). Leave out the "defined()" and test again a value, depending on your macros, like

#if DEBUG==0 && MACOS==1
#error "Spam!"
#endif

Upvotes: 3

Michael Dorgan
Michael Dorgan

Reputation: 12515

#if !DEBUG && MACROS

or 

#if !DEBUG & !MACROS

depending on what you are looking for. defined() can also help

#if !defined(DEBUG) && defined(MACROS)

Upvotes: 2

Mark B
Mark B

Reputation: 96233

I think something like #if !defined(DEBUG) && defined(MACOS) should do it.

Upvotes: 13

Edward Strange
Edward Strange

Reputation: 40849

#ifndef and #if do different things so it depends on what you want. #ifndef is true when there is no defined preprocessor symbol that matches the name following. #if is true when the following preprocessor expression evaluates to non-zero.

You can use the standard && and || operators.

Upvotes: 3

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