[Spice-devel] [PATCH v2 2/2] Avoid clang warnings on casts with stricter alignment requirements

[Victor Toso]

On Tue, May 23, 2017 at 11:51:01AM +0200, Christophe Fergeau wrote:
> On Thu, May 18, 2017 at 03:24:41PM +0200, Christophe de Dinechin wrote:
> > > 
> > >> @@ -140,6 +140,41 @@ size_t spice_strnlen(const char *str, size_t max_len);
> > >> 
> > >> #endif
> > >> 
> > >> +/* Cast to a type with stricter alignment constraints (to build with clang)
> > >> */
> > >> +extern void spice_alignment_warning(const char *loc, void *p, unsigned sz);
> > >> +extern void spice_alignment_debug(const char *loc, void *p, unsigned sz);
> > >> +
> > >> +static inline  void *spice_alignment_check(const char *loc,
> > >> +                                           void *ptr, unsigned sz)
> > >> +{
> > >> +#ifndef NDEBUG
> > >
> > > I like the debug idea but I think that currently NDEBUG is never defined.
> >
> > I read that package maintainers often build the released version by
> > doing ./configure CFLAGS=-DNDEBUG, and that it’s considered “principle
> > of least surprise” to use NDEBUG rather than something
> > package-specific for that purpose.
> >
> > That being said, I checked our .spec file, and I don’t see NDEBUG
> > being set in there. That would be the logical next step.
>
> I only see -DNDEBUG being defined for cmake builds in rpm --showrc, and
> none of my 250 spec files have a -DNDEBUG in them, so I would not expect
> this to be set. I think we have SPICE_DEBUG already which might make
> sense, another alternative would be to have a --enable-alignment-debug,


> or something like glib (SPICE_XXX_DEBUG=alignment:foo:bar)

Just to point out that we have a bug for this [0] and IMHO it would be
the best approach but it would take some effort to have it besides the
glib that we would need is 2.50 (current required is 2.36)
[0] https://bugs.freedesktop.org/show_bug.cgi?id=91838

Cheers,
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