[PATCH] FAT library support for libatomic, libgfortran, libgomp, libstdc++

[Iain Sandoe]

Hi David,

thanks for working on this!

David Edelsohn <dje.gcc@gmail.com> wrote:

> [I'll start by repeating what I wrote about a similar libgcc change to
> provide background and context.]
>
> When AIX added 64 bit support, it implemented what Apple MacOS Darwin
> calls "FAT" libraries for its equivalent functionality -- both 32 bit
> and 64 bit objects (or shared objects) are co-located in the same
> archive.  GCC on AIX historically has followed the GCC multilib
> directory hierarchy approach with separate directories and archives
> for each multilib.

End-user builds of GCC on Darwin also currently follow the “GCC multilib”
pattern;  However when and where GCC libraries were installed by Apple
they are already FAT versions (built outside the GCC build system).

… which fortuitously means that a FAT GCC library set is compatible with
the existing system implementations.

Of course that’s an initial reaction - and I/We will need to discuss with the
‘downstreams’ (macports, fink, homebrew) as to whether a switch needs
some transition - or would cause problems.

Given we anticipate a confiuration flag to disable this mode, it seems we
can cover most reasonable concerns.

> libstdc++-v3/
>        * Makefile.am (tmake_file): Build and install AIX-style FAT libraries.
>        * Makefile.in: Regenerate.
>        * configure.ac (tmake_file): Substitute.
>        * configure: Regenerate.
>        * configure.host (aix*): Define tmake_file.
>        * config/os/aix/t-aix: New file.
>        * empty.mk: New file.

As a “proof of principle, quick hack” I used the following fragment for  
libstdc++
on Darwin; this means that the same fragment would work for X86 and PPC
- and (in principle) would work for as many sub-archs as we elected to build.

My only concern in the short-term is about dependencies; is it defined that
the MULTIBUILDTOP case cannot be active until all the deps are built?

(the libgcc_s case for Darwin which is already FAT is more complex but does
  have rules for the components to be built first).

I haven’t tried to implement the FAT CRTs so far - but I suspect that those  
are
going to use simple linear rules.

thanks
Iain

====

ifeq ($(MULTIBUILDTOP),)
MAJOR=$(firstword $(subst :, ,$(libtool_VERSION)))
OTHER=$(shell for d in $(MULTIDIRS); do echo  
"../$$d/$(PACKAGE)-v3/src/.libs/$(PACKAGE).$(MAJOR).dylib "; done)
all-local:
	lipo -create -output src/.libs/$(PACKAGE).$(MAJOR).f.dylib src/.libs/$(PACKAGE).$(MAJOR).dylib $(OTHER)
	mv src/.libs/$(PACKAGE).$(MAJOR).f.dylib src/.libs/$(PACKAGE).$(MAJOR).dylib
endif