Reason for __ aliases of variables

[Joseph Myers]

On Tue, 7 Mar 2017, Florian Weimer wrote:

> We have some global variables in glibc which have internal __ aliases (e.g.,
> daylight and __daylight).  Why do we do this?

As discussed in the signgam context: if the __ alias is exported at a 
public symbol version, as well as the non-__ version as a weak alias, and 
glibc internally only references the __ version, then: if an application 
references the variable without defining its own copy then the application 
will end up with a dynamic relocation against the __ alias (thanks to 
static linker magic), while if it defines its own copy then that copy will 
be separate.  So this provides namespace protection.

-- 
Joseph S. Myers
joseph@codesourcery.com