Re: Compat symbols in abilist files

[Joseph Myers <joseph at codesourcery dot com>]

On Wed, 19 Apr 2017, Carlos O'Donell wrote:

> > I'd consider whether a symbol is a compat symbol to be part of the API, 
> > not the ABI; I don't think it belongs in these files.
> > 
> > It may well make sense to be able to assert that a particular symbol is 
> > not available for new programs to link against, for either static or 
> > dynamic linking.  Or that any given symbol has at most one non-compat 
> > version, in at most one library, except for cases (if any) explicitly 
> > whitelisted as deliberately having public versions in more than one 
> > library.
>  
> Could you expand on why you think this is not part of the ABI?

The ABI is about what (already linked) binaries (executables and shared 
libraries) work with a given glibc installation.  Whether or not a symbol 
is a compat symbol does not affect which executables and shared libraries 
work with it.  It affects what source code can be built and linked with 
that glibc, which is an API issue, not an ABI one.

(The interface to .o files is not expected to be stable, if e.g. one glibc 
version uses an implementation-namespace function in an inline function in 
a header, but a subsequent version removes that inline function and 
changes that symbol to a compat symbol.)

-- 
Joseph S. Myers
joseph@codesourcery.com