CODEWITHSUNDEEP
c++c
SKPS
SKPS

Reputation: 5835

code inside #ifdef is included in runtime or during compilation itself?

I am using #define ENABLE_FLAG inside C++ code and correspondingly trying to include a section of code, while ENABLE_FLAG is defined.

My question is, the particular set of code inside

#ifdef ENABLE_FLAG
....setofcode....
#endif

is evaluated during runtime through #ifdef check or compiler itself sees the ENABLE_FLAG during compilation and includes the code?

Upvotes: 2

Views: 2120

Answers (2)

jim mcnamara
jim mcnamara

Reputation: 16389

#define settings are compile time, and persist during run time.

Upvotes: 2

John Zwinck
John Zwinck

Reputation: 249394

#ifdef and all those other things you see with a # as the first character on the line are "C preprocessor directives." These are handled even before compilation proper. So there will be no runtime decision made at all--the enabled/disabled block of code is decided at the earliest part of the build process.

Upvotes: 6

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