[Bug target/47032] libgfortran references complex long double functions missing on AIX

[sgk at troutmask dot apl.washington.edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47032

--- Comment #3 from Steve Kargl <sgk at troutmask dot apl.washington.edu> 2010-12-21 18:37:21 UTC ---
On Tue, Dec 21, 2010 at 05:07:53PM +0000, dje at gcc dot gnu.org wrote:
> This is an interaction / assumption problem between the target (AIX) and
> libgfortran.  libgfortran previously built with GCC 4.4 s, this is a regression
> because libgfortran is relying on more OS features without providing an
> alternative.  And disabling all long double support (which works in G++) or
> disabling libgfortran on AIX because of this issue seems like a bad options.
> 

libgfortran/configure.ac has lines of the form (note I wrapped the line)

AC_CHECK_LIB([m],[copysignl],[AC_DEFINE([HAVE_COPYSIGNL],[1],\
   [libm includes copysignl])])

So, configure is already checking if libm contains the
the "long double functions".  The problem appears to be
that AC_CHECK_LIB is a compile only test, and these tests
appear to pass on AIX.  AIX rquires a link time test to
either unseti, e.g., HAVE_COPYSIGNL or configure in general
should do a link time tests instead of a compile time tests
to ensure the HAVE_* macros are unset.