Is it OK to put a standard, pure C header #include directive inside a namespace?
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Published on 2012-09-07T19:33:55Z
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2012/09/07
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I've got a project with a class log
in the global namespace (::log
).
So, naturally, after #include <cmath>
, the compiler gives an error message each time I try to instantiate an object of my log class, because <cmath>
pollutes the global namespace with lots of three-letter methods, one of them being the logarithm function log()
.
So there are three possible solutions, each having their unique ugly side-effects.
- Move the log class to it's own namespace and always access it with it's fully qualified name. I really want to avoid this because the logger should be as convenient as possible to use.
- Write a
mathwrapper.cpp
file which is the only file in the project that includes<cmath>
, and makes all the required<cmath>
functions available through wrappers in anamespace math
. I don't want to use this approach because I have to write a wrapper for every single required math function, and it would add additional call penalty (cancelled out partially by the-flto
compiler flag) - The solution I'm currently considering:
Replace
#include <cmath>
by
namespace math {
#include "math.h"
}
and then calculating the logarithm function via math::log()
.
I have tried it out and it does, indeed, compile, link and run as expected. It does, however, have multiple downsides:
- It's (obviously) impossible to use
<cmath>
, because the<cmath>
code accesses the functions by their fully qualified names, and it's deprecated to use in C++. - I've got a really, really bad feeling about it, like I'm gonna get attacked and eaten alive by raptors.
So my question is:
- Is there any recommendation/convention/etc that forbid putting include directives in namespaces?
Could anything go wrong with
- diferent C standard library implementations (I use glibc),
- different compilers (I use g++ 4.7, -std=c++11),
- linking?
- Have you ever tried doing this?
- Are there any alternate ways to banish the math functions from the global namespace?
I've found several similar questions on stackoverflow, but most were about including other C++ headers, which obviously is a bad idea, and those that weren't made contradictory statements about linking behaviour for C libraries. Also, would it be beneficial to additionally put the #include <math.h>
inside extern "C" {}
?
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