well namespaces are a good inclusion in c++ to avoid name pollution.
but take this example:
see my class is secure in namespace, but what about the #defined sym used to preventCode:#ifndef MYHEADER #define MYHEADER namespace mynamespace2007 { class myclass { int myint; }; } #endif
multiple inclusion. is it not as likely as a class to make a name conflict? is there a way to avoid
header defines name pollution?
Use a really long and randomized name. MS VC++ should create a long GUID name for you, but when doing it myself, I just do something like this:
<FILENAME>_H_INCLUDED_<MONTH>_<DAY>_<YEAR>
You can include Hour, Minute & Second if you want, but that's too much typing for me.
Ex.: FILEUTIL_H_INCLUDED_OCT_15_2007
hmm... but it seems to me that if mynamespace2007 is a suitable namespace name, MYNAMESPACE2007_MYHEADER_H should be a suitable name for a header inclusion guard.
Look up a C++ Reference and learn How To Ask Questions The Smart WayOriginally Posted by Bjarne Stroustrup (2000-10-14)
Macros generally ignore namespaces. That's one of the reasons to avoid them as much as possible.
In the case of header guards, where usability is not an issue, it's easy to use long, unambiguous names. I typically form my header names of project name, full in-project path of the file, and the suffix _SR_H to distinguish it from other people's headers.
All the buzzt!
CornedBee
"There is not now, nor has there ever been, nor will there ever be, any programming language in which it is the least bit difficult to write bad code."
- Flon's Law
From Qt sources ...
They don't seem to worry too much about it at Qt.Code:#ifndef QBACKINGSTORE_P_H #define QBACKINGSTORE_P_H ; ... #endif #ifndef QPAINTER_H #define QPAINTER_H ; ... #endif #ifndef QCOLOR_H #define QCOLOR_H ; ... #endif
Oh? How many other projects would you expect to #define a pile of macro names starting with the letter Q, followed by a word in upper case, and ending with _H? And, among those, how many would you expect to #define a macro named QPAINTER_H?
I could say the same thing about names of standard C/C++ classes & functions which are all lower-case. I always use mixed case for my stuff. But then again, if I use 3rd party stuff, they might use all lower-case (or maybe the same name as one of my own function/classes). Which is why we have namespaces to make the names longer and harder to collide (and we have the using keyword so we can type less in places where we know it's safe to do so).
