Re: [PATCH 19/24] errno may not be a gobal R/W variable, use a local variable instead (fix build on NetBSD)

[Manuel Bouyer <bouyer@xxxxxxxxxxxxxxx>]

On Tue, Dec 29, 2020 at 03:38:53PM +0100, Roger Pau Monné wrote:
> On Mon, Dec 14, 2020 at 05:36:18PM +0100, Manuel Bouyer wrote:
> > ---
> >  tools/xenpaging/xenpaging.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> > 
> > diff --git a/tools/xenpaging/xenpaging.c b/tools/xenpaging/xenpaging.c
> > index 33098046c2..39c8c83b4b 100644
> > --- a/tools/xenpaging/xenpaging.c
> > +++ b/tools/xenpaging/xenpaging.c
> > @@ -180,10 +180,11 @@ static int xenpaging_get_tot_pages(struct xenpaging 
> > *paging)
> >  static void *init_page(void)
> >  {
> >      void *buffer;
> > +    int rc;
> >  
> >      /* Allocated page memory */
> > -    errno = posix_memalign(&buffer, XC_PAGE_SIZE, XC_PAGE_SIZE);
> > -    if ( errno != 0 )
> > +    rc = posix_memalign(&buffer, XC_PAGE_SIZE, XC_PAGE_SIZE);
> > +    if ( rc != 0 )
> 
> I think the point of setting errno here is because posix_memalign
> doesn't set it and instead returns an error code. The caller of
> init_page uses PERROR in order to print the error which his expected to
> be in errno.

I understand this. But on NetBSD, errno is:
#define errno (*__errno())

(I think this is related to thread-safety).

> 
> I don't think this is the only place in Xen code that errno is set, why
> are the others fine but not this instance?

probably this code is not used on NetBSD ?

-- 
Manuel Bouyer <bouyer@xxxxxxxxxxxxxxx>
     NetBSD: 26 ans d'experience feront toujours la difference
--