best-practice on C header files with #ifndef #define #endif

Question

what is concerned best practice regarding the following \"pattern\"?

#ifndef BLAFOO_H
#define BLAFOO_H
/* ...
 * ...
 */
#endif /* BLAFOO_H */

Answer 1

The only real requirement is that it won't conflict with another project that uses the same name for its file. For all of the projects I've seen, it usually completely quantifies the namespace (or whatever folder the file is in for C) along with the project name. Sometimes it includes the date the file was created too.

So if you're working on project ABC in folder DEF today, then you could do:

#ifndef ABC_DEF_BLAFOO_H_05_30_2010

And this is very unlikely to conflict with anything.