Re: flags for different fortran compilers

[Ralf Wildenhues]

Hello,

* Eve-Marie Devaliere wrote on Mon, Jan 31, 2011 at 05:34:47PM CET:
> I am trying to replicate the install of an existing package using autoconf.
> We need the package to be able to compile with a wide variety of
> compilers. In the original setup this was done by the make.macros file
> that would give a list of flags for each compiler.
> From what I understand autoconf has a few built in macros that help with
> the choice of flags such as AC_FC_FREEFORM, but unless I am missing
> something that won't cover all the flags. What is then the recommended
> way to handle this? I could have a bunch of 'case' in my configure.ac
> file but I wanted to see if there wouldn't be a more elegant way... I am
> new to fortran too so that may sound crazy but couldn't there be a
> library of flag for known fortran compiler that autoconf could select on
> the fly like for the free form one?

Which kinds of flags do you need support for?

The "Autoconf Way" of implementing things, when there isn't a predefined
macro for some feature, is to try out a set of known compiler switches
and select the first one that has the desired features.  For example,
the AC_FC_FREEFORM macro tries to compile a small free-form source file,
and passes one of a few known compiler flags that enable free form.  It
picks the first one that works.

If you can formulate your needs in such a way, then the next hurdle is
to overcome the M4 language and a few Autoconf building block macros
like AC_COMPILE_IFELSE and AC_LINK_IFELSE.  We can help with the latter
if the former is clear.

Cheers,
Ralf