glibc 2.19 - asyn-signal safe TLS and ASan.

[Joseph S. Myers]

On Fri, 24 Jan 2014, Paul Pluzhnikov wrote:

> I *think* exporting these symbols for 2.19 is the right thing to do.

I don't think such symbols are a good idea for the public interface (as 
opposed to GLIBC_PRIVATE) - and in any case, symbols should not be added 
to the public interface during release freeze, unless only for an 
architecture for which you are doing the release testing, because adding 
public symbols means updating all the ABI baselines and retesting in all 
relevant configurations.

Specifically, I think of the present solution as an interim solution, 
until someone implements TLS in a way that does the allocation at 
pthread_create / dlopen time and avoids the possibility of allocation 
failure where an error cannot be returned.  And it's not obvious that such 
non-lazy allocation would need signal-safe allocators at all - meaning 
that glibc built for new architectures, not needing compatibility for any 
old binaries relying on overcommit for TLS variables, could then avoid 
including those allocators (presuming we keep them at all to make 
allocation for existing binaries signal-safe).

Exporting symbols at GLIBC_PRIVATE is not a good solution for externally 
maintained projects because those shouldn't be using GLIBC_PRIVATE symbols 
at all.

-- 
Joseph S. Myers
joseph@codesourcery.com