[Bug libstdc++/13207] New: <iostream> header and _XOPEN_SOURCE=500

[rdesai at legato dot com]

On an alpha (OSF1) V5.1 system, when I try to compile a C++ source that 
includes the STL <iostream> header, if I define -D_XOPEN_SOURCE=500 (or 
anything greater than or equal to 420, for that matter), I get the following 
errors:

In file included 
from /opt/TWWfsw/gcc332/include/c++/3.3.2/bits/locale_facets.tc
c:41,
                 from /opt/TWWfsw/gcc332/include/c++/3.3.2/locale:47,
                 from /opt/TWWfsw/gcc332/include/c++/3.3.2/bits/ostream.tcc:37,
                 from /opt/TWWfsw/gcc332/include/c++/3.3.2/ostream:535,
                 from /opt/TWWfsw/gcc332/include/c++/3.3.2/iostream:45,
                 from x.cpp:3:
/opt/TWWfsw/gcc332/include/c++/3.3.2/cmath: In function `long double 
   std::acos(long double)':
/opt/TWWfsw/gcc332/include/c++/3.3.2/cmath:194: error: `::acosl' undeclared 
   (first use here)

Which is followed by many additional lines with "long double" math functions.

The reason that _XOPEN_SOURCE >= 420 triggers it, is that this causes 
standards.h to automatically set _XOPEN_SOURCE_EXTENDED, which in turn causes 
math.h not to define the "long double" math functions.

So I am not sure if the problem is in math.h, for not defining the functions 
or in cmath for not dealing with it properly.  Regardless, setting 
_XOPEN_SOURCE=420 or higher should not cause the STL to not compile.

-- 
           Summary: <iostream> header and _XOPEN_SOURCE=500
           Product: gcc
           Version: 3.3.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: libstdc++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rdesai at legato dot com
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: alphaev56-dec-osf5.1
  GCC host triplet: alphaev56-dec-osf5.1
GCC target triplet: alphaev56-dec-osf5.1


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13207