I have been seeing code like this usually in the start of header files:
#ifndef HEADERFILE_H #define HEADERFILE_H
And at the end of the file is
#endif
What is the purpose of this?
Those are called #include guards.
Once the header is included, it checks if a unique value (in this case HEADERFILE_H
) is defined. Then if it's not defined, it defines it and continues to the rest of the page.
When the code is included again, the first ifndef
fails, resulting in a blank file.
That prevents double declaration of any identifiers such as types, enums and static variables.
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