Hi,
While research requirements for binary package soname dependencies [1],
I found that the NEEDED.ELF.2 data that portage generates contains
insufficient information to uniquely distinguish all of the multilib
ABIs that may be present on a given system [2]. In order to correctly
handle multilib ABIs for binary package soname dependencies,
preserve-libs, and other possible applications involving GLEP 64 [1], we
will need more information than is currently recorded in NEEDED.ELF.2.
In order to solve this problem, I propose that we extend NEEDED.ELF.2 to
include a new field containing a multilib ABI identifier. The extension
will be backward-compatible, and NEEDED.ELF.2 will only need to be
regenerated on systems with multilib ABIs that are otherwise
indistinguishable (multilib x32 and mips systems).
The naming convention for the multilib ABI identifiers can be derived
from the set of abi_* USE flags that has been established by the
gx86-multilib project [4]. For example, if we exclude the abi_ prefix,
and apply this convention to all supported architectures, then the
complete set of multilib ABI identifiers will be as follows:
alpha_{32,64}
arm_{32,64}
hppa_{32,64}
ia_{32,64}
m68k_{32,64}
mips_{eabi32,eabi64,n32,n64,o32,o64}
ppc_{32,64}
s390_{32,64}
sh_{32,64}
sparc_{32,64}
x86_{32,64,x64}
The ABIs referenced by some of the above *_32 and *_64 identifiers may
be imaginary, but they are listed anyway, since the goal is to establish
a naming convention that is as consistent and uniform as possible. The
OS is notably absent from these identifiers, since OS-independence is
one of the goals. The assumption is that, for a given installation, we
are only interested in tracking multilib ABIs for a single OS.
I have attached a python script to bug 534206 [2] that can serve as a
reference implementation, demonstrating how a file's ELF header can be
used to compute a suitable multilib ABI identifier.
Please respond with any feedback that you may have about this proposal.
[1] http://thread.gmane.org/gmane.linux.gentoo.devel/94145
[2] https://bugs.gentoo.org/show_bug.cgi?id=534206
[3] https://wiki.gentoo.org/wiki/GLEP:64
[4] https://wiki.gentoo.org/wiki/Gx86-multilib
--
Thanks,
Zac
