Re: libtool - building both 32 and 64-bit members for archives in one "pass"

[Michael Haubenwallner]

Hi Michael,

On 01/19/2016 09:44 PM, Michael Felt wrote:
> L.S.,
> 
> If I understand the documentation correctly libtool places non-shareable 
> members (.o files) in the src directory
> and "shareable aka PIC objects in src/.libs". However, libtool makes only one 
> size of objects - either 32-bit or 64-bit.
> 
> As "aixtools" I am trying to package (common) opensource projects - and 
> mainly I have done so as as 32-bit only and was not bothered by the lack
> of 64-bit build issues. Recently there are packages that may only work well 
> in 64-bit mode (e.g., R language) and I have started to package
> in 64-bit as well.
> 
> As part of my research I see that Linux distros seem to use 
> .../lib/libsomething* and .../lib64/libsomething* for 32 and 64-bit 
> (respectively) library
> packaging. The AIX convention - as you may, or may not know, is not to have 
> multiple .so files in two directories but to have one .../lib/libsomething.a
> with multiple members as static and/or shareable objects. The same object 
> name may be used multiple times, although the legacy convention is to
> use shr.o as a shared object of multiple .o members and shr64.o for the same 
> .o files - but compiled in 64-bit mode).
> 
> I am wondering - and willing to work on - with assistence - an addition to 
> the .lo target such that both 32 and 64 bit (shared) objects are made
> for inclusion in a single .a archive - to be compareable with a library as it 
> would be released by IBM AIX developers/labs.

IMO, there is no point in having multilib support within libtool for AIX only.
If ever, multilib support inside libtool should be implemented in some generic
way - to allow for porting to Linux and others eventually.

Instead, for the time being even on AIX, it is up to the package manager to
separately compile the package in 32-bit and 64-bit mode, and then merge the
members of both the 32-bit Archive Library and the 64-bit Archive Library into
one single Archive Library. Agreed this is a little tricky, but possible.

However, this works as long as you have libtool to create Archive Libraries
at all - which is the default when LDFLAGS does not contain "-brtl".

My 2 cents,
/haubi/

PS: Probably worth a note: Since libtool-2.4.4 there is the "--with-aix-soname"
configure option for optional filename-based shared library versioning on AIX,
which is designed to work with above multilib merging strategy as well.