[CMake] Checking function or symbol in namespace

[Mateusz Loskot]

Jed Brown wrote:
> On Thu, 21 Jan 2010 15:44:43 +0000, Mateusz Loskot <mateusz at loskot.net> wrote:
>> Why it can not work, actually?
> 
> C++ does name mangling so it's difficult to determine what the symbol
> actually is (you have to know about various classes and templates that
> may be in scope), therefore the interface would look a bit different.

After some testing I did yesterday, I would add that one of the problems
making it difficult to provide elegant macro checking C++ functions
is the fact that in C++ functions can be overloaded.

I suppose that the only flexible, robust and also elegant way to provide
cross-platform macros for detecting C++ (also with mixed in C99, TR1,
C++0x, etc.) features is to develop one macro per feature (function,
macro, etc.)

For instance,

1) check_cxx_fabs - checks std::fabs in <cmath>, optionally falls back
to ::fabs in <math.h> if a systems has problems with std:: (i.e. Visual
C++ 6.0)

2) check_cxx_isnan - tries if C++ impl. has C99 compatibility [1]
additions, on some systems available as std::tr1::isnan on others as
std::isnan, if fails, then falls back to system specific functions like
_isnan() form Visual C++ or __inline_isnand from XCode, etc.

It would probably generate large number of small macros, but I can't see
a more robust and flexible way to make such checks in reusable form.
Perhaps it could make into the CMake distribution one day :-)

[1] http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2004/n1568.htm

Best regards,
-- 
Mateusz Loskot, http://mateusz.loskot.net
Charter Member of OSGeo, http://osgeo.org