2007/559: new symbol visibilities - EXPORTED, SINGLETON, and ELIMINATE

[Nicolas Williams]

On Tue, Oct 02, 2007 at 09:51:21AM -0700, Rod Evans wrote:
> Just for the record, there's a cut-and-paste error:
> 
> > As this is a "public" ELF field, the proposal was passed around several
> > > ELF vendors.  See:
> > >
> > >  
> http://groups.google.com/group/generic-abi/browse_thread/thread/1a84adc1566616
> 
> The link should be:
> 
> http://groups.google.com/group/generic-abi/browse_thread/thread/1a84adc15666164
> 
> Bug report 660245 has the correct link.

A few questions:

   Can one interpose on singleton symbols using LD_PRELOAD?  I assume
   yes, or at most that the interposers in the pre-loaded object must be
   labelled singleton as well.

   Will dlsym(RTLD_NEXT, <singleton symbol>) return the next symbol?  Or
   the one bound symbol (it is a singleton, after all)?

   If multiple objects define the same singleton symbol, will dlsym()
   called with a handle for each of those objects resolve the same
   symbol to the first definition, or to each object's version?

   Presumably libraries designed so that multiple versions can be
   present in one process (I think that's feasible, with some
   constraints) must not use singleton symbols.

Nico
--