Re: architecture-independent GNAT project files?

[Ludovic Brenta <ludovic@ludovic-brenta.org>]

Björn Persson wrote on comp.lang.ada:
> >> The way to find out the architecture of a Unix-like system appears to be
> >> to invoke uname, but GNAT project files don't seem to have a shell-out
> >> feature. As far as I can see in the manual the only ways they can get
> >> input is by environment variables and command line parameters. I don't
> >> suppose Gnatmake provides some variable to project files that shows what
> >> the architecture is?
>
> > I don't know if it has, but if any, how that is supposed to work for cross
> > platform developing?
>
> The cross-compiler would know its target platform and would assign that
> value to the hypothetical variable. The project file would then select the
> right library directories for that platform.

Yes. "gcc -v | grep ^Target:" yields the correct information.  I
normally use a minimal Makefile to set up such variables from the
environment and then invoke gnatmake, passing it the variables.

> Such a feature, if done right, could make it possible to write project files
> that would work for anything from ARM to Itanium, but I wasn't planning to
> do that. I'm satisfied if I can support a multilib environment so that i386
> libraries will be selected if someone uses the -m32 parameter on an x86_64
> platform. For true cross-compilation I guess the cross-compiler will
> normally have a completely separate set of libraries, including a separate
> project file directory.

It is my understanding that "gcc -m32" invokes the linker in such a
way (i.e. "ld -melf_i386", "ld -mi386linux" or some such) that it
automatically selects /usr/lib64 instead of /usr/lib.  Is that not the
case?

If I'm right, your problem disappars as far as binary libraries go but
still exists for target-dependent source files.

--
Ludovic Brenta.