PIC

[Barry Smith]

On Wed, 14 Dec 2005, Matthew Knepley wrote:

> Barry Smith <bsmith at mcs.anl.gov> writes:
> 
> >   Hmmm, why should you have a PIC test? Who cares if something
> > has PIC or not? You only thing you care about is that you CAN
> > do what you want to do with it? (In this case I think it is simply
> > that you can build an executable using a shared library PLUS the
> > given library you are testing.)
> >
> >    Barry
> >
> > configure is suppose to be "can I ...?" not "is something ...?"
> 
>   Because the "can I" is VERY erratic. I can build some shared libraries, but
> cannot build others. 

  My understanding is that it can build a basic shared library (stand alone 
with a couple of symbols) BUT cannot build a shared library (and use it) in conjunction
with the MPI libraries. So I fail to understand why you cannot just test this?????
Make a new test that is, exactly the FIRST part of the test

  def checkShared(self, inclu....

up to the code where 

    if not checkLink(includes, body, cleanup = 0, codeBegin = codeBegin, codeEnd = codeEnd, shared = 1):
      if os.path.isfile(configObj.compilerObj): os.remove(configObj.compilerObj)
      self.setCompilers.LIBS = oldFlags
      raise RuntimeError('Could not complete shared library check\nCould not create a shared library using the currently configured shared linker.\nSuggest running with --with-shared=0 if you do not need shared libraries. Otherwise send configure.log to petsc-maint at mcs.anl.gov')

but instead of throwing the silly exception you return 0 here. But if the link 
succeeds you continue the test until 

''' % (boolType, checkCode)
    if finiFunction:
      body += '  if (isInitialized) '+finiFunction+'();\n'
    body += '  return (int) isInitialized;\n'
    codeEnd   = '\n}\n'
    if not checkLink(includes, body, cleanup = 0, codeBegin = codeBegin, codeEnd = codeEnd, shared = 1):
      if os.path.isfile(configObj.compilerObj): os.remove(configObj.compilerObj)
      self.setCompilers.LIBS = oldFlags
      raise RuntimeError('Could not complete shared library check\nCould not create a shared library using the currently configured shared linker.\nSuggest running with --with-shared=0 if you do not need shared libraries. Otherwise send configure.log to petsc-maint at mcs.anl.gov')
      return 0

here instead of the exception return 1 or 0 based on whether the link succeeds.
Do not do the rest of the test.

  I may be missing something but I don't understand why this has to be 
such a difficult thing. We know exactly where things go wrong (based on the log files)
so we write a test specifically for that problem and report failure or success why
make life more complicated.

   Barry

>I do not understand the difference between these libraries
> at the moment, however I DO know that absence of the PIC option causes the error.
> Furthermore, checking this option allows a precise error message rather than a
> guess. Lastly, this is in the configure spirit I believe, because we often test
> the "what" of things, like endianness or the size of void *.
> 
>     Matt
>