libm lacks C99 functions -> no c++11 cmath in libstdc++

[Dmitry Marakasov]

* Steve Kargl (sgk at troutmask.apl.washington.edu) wrote:

> > > > - bad enough by itself, it affects libstdc++ from ports' gcc in such a
> > > >   way that it disables C++11 math completely (along with a lot more
> > > >   other more widely used math functions)
> > > >
> > > >
> > > > - we may probably implement these by calling less-precise
> > > >   erf erfc lgamma tgamma as we do with other functions as we alredy
> > > >   do with some others
> > > 
> > > This, unfortuantely, has already been done, although it may only 
> > > be available in FreeBSD-current.  See src/lib/msun/src/imprecise.c.
> > 
> > I know, it's available on 10.0 as well. However that's not the case for
> > 9.x, for which it's impossible to build c++11 math using software (even
> > if it doesn't use unimplemented functions), neither with system gcc
> > nor with gcc from ports.
> > 
> 
> It's not impossible.  Add whatever C++-fu you need
> that is equivalent to
> 
> #include <math.h>
> #ifndef fool
> #define fool(x)	foo((double)(x))
> #endif

The point was that one should not be required to do something like this
to build std::hypot - using software on FreeBSD.

---
+#define _GLIBCXX_USE_C99_MATH_TR1
+#include <math.h>
+long double erfl(long double x) { return erf(x); }
+long double erfcl(long double x) { return erfc(x); }
+long double lgammal(long double x) { return lgamma(x); }
+long double tgammal(long double x) { return tgamma(x); }
+
 #include <cmath>
 int main() { std::hypot(3.0, 4.0); }
---

-- 
Dmitry Marakasov   .   55B5 0596 FF1E 8D84 5F56  9510 D35A 80DD F9D2 F77D
amdmi3 at amdmi3.ru  ..:  jabber: amdmi3 at jabber.ru    http://www.amdmi3.ru