Re: Fix mcontext_t sigcontext namespace (bug 21457)

[Joseph Myers <joseph at codesourcery dot com>]

On Mon, 26 Jun 2017, Zack Weinberg wrote:

> I'm concerned that this may be a step too far in the direction of POSIX
> conformance at the expense of existing code: specifically, existing code
> that assumes that struct sigcontext and mcontext_t are "compatible"
> types (in the C-standardese sense), not just structures with the same
> set of members.  The most _obvious_ ways this would show up are passing
> 'mcontext_t *' values to functions taking 'struct sigcontext *'
> arguments, or using structure assignment to copy between the two, both
> of which should cause compile failures; but there could be other
> problems (aliasing, perhaps), that only show up at runtime.

Any such assumptions would already not work on x86_64 / x86, where 
mcontext_t is not struct sigcontext.  For that reason, I don't think such 
issues are particularly likely, especially any that don't show up at 
compile time.

-- 
Joseph S. Myers
joseph@codesourcery.com