[petsc-dev] Disabling a header in configure based on a bad link?

[Aron Ahmadia]

Hi folks,

I'm working on a Cygwin64 port of PETSc and I have a question about doing a
specific disable in BuildSystem based on a failing link.

The Cygwin folks provide an fenv.h implementation that (as far as I can
tell), is currently broken due to an undefined FE_DFL_ENV variable.  My
inclination is to disable this functionality in PETSc by declaring that
fenv.h is unavailable if a simple link test fails.  I tried to write a test
like this (in Configure.py)

def configureCygwin(self):
  '''Cygwin specific stuff'''
  # detect problem with missing FE_DFL_ENV symbol in Cygwin64
  if not self.checkLink('#include <fenv.h>', 'fesetenv(FE_DFL_ENV)'):
      self.headers.headers.remove('fenv.h')


I don't think it worked.  Has anybody had experience with *disabling*
functionality in BuildSystem?  Should we be less optimistic about having
the header and only enable it if the test passes?  Where would it go?

Cheers,
Aron
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