Andrew Straw <strawman@...36...> writes:
extern "C" {
int isnan(double);
}Apparently, the upshot is that isnan is a C99 feature and C++ does not
incorporate C99.So, does that mean the above should work on most C++ compilers? (Do
they implement C99 mode when in extern "C" mode?)
What extern "C" does is it disables the C++ name-mangling so you can
refer to C functions. The presence of isnan is a header/library issue,
and apparently the cmath header file in some systems makes sure to
hide isnan. It seems that C99 defines an isnan _macro_, and the above
is assuming that an isnan _function_ exists in the library. The isnan
manual page on OS X states:
HISTORY
3BSD introduced isinf() and isnan() functions, which accepted double
arguments; these have been superseded by the macros described above.
I don't know how widespread these functions are. GNU libc and OS X
have them, and all the world's either Linux or a Mac, right? 
I think we could use the system's isnan macro in a fairly clean way by
performing the following dance (untested, and I don't have an OS X
10.3 system to test on):
#include <math.h>
template<typename T> int mpl_isnan(T arg) { return isnan(arg); }
#include <cmath>
Is it possible in distutils to do autoconf-style compilation tests at
configuration time?
ยทยทยท
--
Jouni