Fixing namespace issues for variables

[Joseph Myers]

On Fri, 23 Oct 2015, Roland McGrath wrote:

> > re_syntax_options (bug 18442) may be a more straightforward case for this 
> > fix, as a pure GNU extension.
> 
> Well, it's simpler only in the sense that there is no conformance issue to
> think about.  It's probably also less sensitive in that the likelihood that
> this identifier is in use in existing application code seems low off hand.
> But I think the primary concern for all the cases is whether it's really OK
> to effectively reserve an identifier for all purposes rather than just for
> external linkage when that identifier was previously available for other uses.

The third case of this issue is stdin, stdout, stderr.  They are already 
macros, unambigously reserved as such - the issue for them (bug 17576) 
being that the existing "#define stdin stdin" with "extern struct _IO_FILE 
*stdin;" is also using them with external linkage when they aren't 
reserved with external linkage, at least if <stdio.h> isn't included.  
But as by far the most widely used variables with this issue, and the ones 
with the most existing ABI complexity around them, a fix for them 
certainly shouldn't be considered straightforward at all.

-- 
Joseph S. Myers
joseph@codesourcery.com