Re: preprocessed F90 using IBM XL F90 compiler

[Ralf Wildenhues]

Hello,

* Dr Magnus Hagdorn wrote on Thu, Apr 20, 2006 at 10:34:48AM CEST:
> On Wed, 2006-04-19 at 09:07 -0700, Noah Misch wrote:
> > On Wed, Apr 19, 2006 at 09:27:12AM +0100, Dr Magnus Hagdorn wrote:
> > > I define symbols using AC_DEFINE which should be passed to the
> > > preprocessor to optionally compile certain parts. This all works fine
> > > except for when the IBM XL f90 compiler is used. This compiler does not
> > > have the -D switch to pass options to the preprocessor and instead
> > > expects -WF,-D.

> > If portability to a wide variety of Make programs is not a priority,
> > the above solution is fine.  Otherwise, try this:
> > 
> >   if AIX_XL
> >     DEFS = `echo @DEFS@ | sed 's/-D[^        ]*/-WF,&/g'`
> >   endif
> > 
> > It does incur a regrettable performance hit.

This approach has several flaws:
- The `echo @DEFS@ | ..` isn't right, as it messes up escaping for the
  shell (try `-DPACKAGE_STRING=\"foo\ 1\"').

- Automake doesn't allow to override its DEFS definition.  It will
  output it anyways currently; so it doesn't help either to

    if AIX_XL
      DEFS = ..
    else
      DEFS = ..
    endif

- Same thing with $(PPF77COMPILE), by the way.  But in my test the
  Automake definition gets output before the user one, so you could
  use this hack:

if AIX_XL
PPF77COMPILE = $(F77) $(DEFS:-D%=-WF,-D%) $(DEFAULT_INCLUDES) $(INCLUDES) \
        $(AM_CPPFLAGS) $(CPPFLAGS) $(AM_FFLAGS) $(FFLAGS)
else
PPF77COMPILE = $(F77) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) \
        $(AM_CPPFLAGS) $(CPPFLAGS) $(AM_FFLAGS) $(FFLAGS)
endif

  This uses Automake internals, though, and may happily break with the
  next Automake version (or even with the same, under different
  conditions than the one I tested), so consider yourself warned.
  (Erm, there should be better $(FC) support here, I guess..)

> unfortunately, I get in both cases this error message:
> src/Makefile.am:51: DEFS was already defined in condition TRUE, which
> includes condition FC_XL ...
> configure.in:10: ... `DEFS' previously defined here
> which is AM_INIT_AUTOMAKE

Yes, but Automake still completes and outputs a Makefile.in, just that
the order isn't right in that case.

> > Ideally, Autoconf should test -D and -WF,-D and use the one that works.  
> > Since
> > the C compiler will probably still need -D, we would create a DEFS variable 
> > for
> > each preprocessed language: CDEFS, CXXDEFS, F77DEFS, FCDEFS.  Automake would
> > need changes to take advantage of the new variables, but Autoconf could
> > substitute DEFS = ${CDEFS} for backward-compatibility.
> > 
> yes. grrr, the IBM Fortran XL compiler is just a total pain to support.
> Everything is odd.

The simplest solution would probably be to write a wrapper for this
compiler, and put it early in the user's PATH.  Below is a suggestion.
(Note that `-D' is a legitimate flag for xlf90, so it should not be
escaped.)

Cheers,
Ralf

#! /bin/sh
# xlf90-wrapper

for arg
do
  case $arg in
  -D)  set x "$@" "$arg";;
  -D*) set x "$@" "-WF,$arg";;
  *)   set x "$@" "$arg";;
  esac
  shift # x
  shift # $arg
done

exec /usr/bin/xlf90 "$@"