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Re: Fix mcontext_t sigcontext namespace (bug 21457)

On Tue, 27 Jun 2017, Szabolcs Nagy wrote:

> > diff --git a/sysdeps/unix/sysv/linux/aarch64/sys/ucontext.h b/sysdeps/unix/sysv/linux/aarch64/sys/ucontext.h
> > index 4f602fc..90d0c42 100644
> > --- a/sysdeps/unix/sysv/linux/aarch64/sys/ucontext.h
> > +++ b/sysdeps/unix/sysv/linux/aarch64/sys/ucontext.h
> > @@ -24,10 +24,15 @@
> >  #include <features.h>
> >  
> >  #include <bits/types/sigset_t.h>
> > -#include <bits/sigcontext.h>
> this may break software that rely on declarations from
> asm/sigcontext.h to be visible in sys/ucontext.h (e.g.
> struct fpsimd_context ?), but i don't know if this is
> actually the case.

They can of course include <signal.h> (or <asm/sigcontext.h> directly).  
It's possible to keep the include, conditioned on __USE_MISC, just not 
clear that's worthwhile.

> i find the c++ abi break problematic.
> i would not expect mcontext_t to be common argument
> in c++ code, but it's a moderately dangerous change,
> while the status quo is not too bad.

For some previous patches in this series, changing stack_t and ucontext_t, 
Florian checked there were no affected mangled names in Fedora, as 
evidence for such problems being rare.  Such a check might be worthwhile 
here (remembering that what is being looked for is architecture-specific, 
but on x86_64 / x86 the mangled name is already mcontext_t and would not 
change because there aren't namespace issues there).

Joseph S. Myers

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