4 ms·
It's only MxN if there is no use of the "#ifndef _HEADER_H" workaround that he mentioned earlier. There still is a processing cost for evaluating the instructi
by VMG 14y ago
It's only MxN if there is no use of the "#ifndef _HEADER_H" workaround that he mentioned earlier.
There still is a processing cost for evaluating the instruction
- lttlrck 14y agoFor GCC this is highly optimized: "The preprocessor notices such header files, so that if the header file appears in a subsequent #include directive and FOO is defined, then it is ignored and it doesn't preprocess or even re-open the file a second time. This is referred to as the multiple include optimization." http://gcc.gnu.org/onlinedocs/cppinternals/Guard-Macros.html http://gcc.gnu.org/onlinedocs/cppinternals/Guard-Macros.html
- pjmlp 14y agoExcept that the contents of foo.h might be different depending on where it is being included.