difask's blog

By difask, 10 years ago, translation, In English

I have seen in many codes that structure like following is using :

#ifdef something

...

#endif

Where can I set up "something"? I use CodeBlocks. Thank you!

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10 years ago, # |
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This can be done in the compiler settings of your IDE. Usually they allow you to pass some arguments to the compiler invocation. You need to pass the argument:

-D something

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10 years ago, # |
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you could enable by putting #define something 1 before that #ifdef :

#define something
#ifdef something
...
#endif
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10 years ago, # |
Rev. 3   Vote: I like it +2 Vote: I do not like it

This is a simple example for #ifdef, #ifndef and #else you can also have #elif which works like else if and there is #if that works like if;

#define HelloWorld

#ifdef HelloWorld
#define ByeWorld
// This line will be executed
#else
#define HelloWorld
// This line won't be executed
#endif

#ifndef HolaMundo
#define HolaMundo
// This line will be executed
#else
#define AdiosMundo
// This line won't be executed
#endif
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10 years ago, # |
  Vote: I like it +13 Vote: I do not like it

For Codeblocks: Settings -> Compiler.

If you invoke gcc manually: g++ -DSOMETHING ...