Can #if pre-processor directives be nested in C ++?

Question

I have a question about preprocessor directives in C ++:

For example:

#ifndef QUESTION //some code here #ifndef QUESTION //some code here #endif #endif

Can we use it that way and can the C ++ compiler match ifndef and endif right way?

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c ++ c-preprocessor preprocessor-directive

user707549 Jul 13 '11 at 11:52

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3 answers

Yes, you can #if / #endif blocks. Some styles of C-style will tell you to write

 #ifdef CONDITION1 # ifdef CONDITION2 # endif #endif

using spaces to indicate the level of nesting.

+34

Fred Foo Jul 13 '11 at 11:55

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In your code, the #ifndef QUESTION section will be dropped if you are not #UNef QUESTION.

Good luck

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bert-jan Jul 13 '11 at 11:59

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Armen Tsirunyan · Accepted Answer · 2011-07-13 11:54

Yes we can. The #endif operator matches the previous #if #ifdef or #ifndef , etc., for which there was no corresponding #endif .

eg.

 #if ----------| #if -----| | #endif ---| | #endif --------|