[PATCH v2] shlib: Create a default symbol version on Linux-like ELF

[Adam Jackson]

(apologies for the slow response)

On Thu, 2014-07-31 at 23:25 -0700, Eric Christopher wrote:
> Ah thanks Sylvestre. Wonder why gold doesn't have the option? 

If I'm being uncharitable: because gold is unfinished demoware.

> Adam: feel like a configure and cmake time check for the option?

Not really?  Not because I don't want to do the work, because it's a bad
idea to make it conditional.  Binaries linked against a symbol-versioned
libLLVM will fail to run when installed on a system that decided to
build an unversioned libLLVM.  For the binary to be portable it would
need to link against an unversioned libLLVM, but besides imposing
additional complexity on the app developer it would defeat the purpose
of the change: the unversioned binary would resolve symbols against
whichever library happens to be first in the ELF search order and
provides the symbol name, instead of being assured of getting the ABI it
was built against.

Probably better is to pass --version-script, which both bfd and gold
appear to support.  lld does not yet, but I guess that's not a problem
since it also doesn't support --no-undefined which the shlib build is
already using.  Are there other linkers people think are worth caring
about?

- ajax