Re: Multilib and Linux.

[hjl@lucon.org (H.J. Lu)]

> In terms of EGCS it should be fine.  We have used multilibbing on ARM in the 
> past to support both 26-bit and 32-bit ABIs, and I've also considered adding 
> extra ABIs for floating-point related things.  At the moment the multilib stuff 
> is turned off in the EGCS config files though because having it enabled means 
> that everybody who wants to build the compiler needs to have both flavours of 
> build environment set up (including glibc and so on).

That is the easy problem.

> 
> The only place I can foresee problems is with shared libraries.  This isn't 

It is more than just shared libraries.

> really a bridge we've crossed on the ARM yet.  We have EF_* values to tag the 
> different ABIs in the ELF header so in theory the dynamic linker can be taught 
> to only pull in the right sort of libraries, probably using the same hook that 
> distinguishes libc5 vs libc6 shared objects.
> 

Have you thought that every single .o/.a/.so file used by linker and
run-time linker may have to have a copy for each ABI if ABIs are
totally incompatible? How do you deal with XFree86, KDE, GNOME, ....
Where do you put those files for linker and run-time linker to find?
What is the default ABI? ALL your Makefiles have to support multilib.
It is a mess to me.



-- 
H.J. Lu (hjl@gnu.org)