Tom Browder <tom.browder@xxxxxxxxx> writes: > The cpp manual states: > > <quote> > CPP optimizes even further. It remembers when a header file has a > wrapper `#ifndef'. If a subsequent `#include' specifies that header, > and the macro in the `#ifndef' is still defined, it does not bother to > rescan the file at all. > </quote> > > Does that mean (1) the file is reopened but not scanned, or (2) does > it mean the file is not even opened? It seems that (1) is probably > the correct answer, but I'm looking for confirmation. I believe that the file is not even opened. > It makes a slight difference efficiency-wise, and there is a cpp > "#pragma once" that will definitely avoid reopening the header after > the first time it's read. #pragma once is considered to be obsolete, because the default behaviour is simpler. Ian
