Re: [Qemu-devel] [RFC 15/15] [test only] Use 'Error *err[static 1]' instead of 'Error **errp' to catch NULL errp arguments

[Eduardo Habkost <ehabkost@redhat.com>]

On Tue, Jun 27, 2017 at 03:12:25PM -0500, Eric Blake wrote:
> On 06/19/2017 08:26 AM, Eduardo Habkost wrote:
> 
> >> Is gcc's __attribute__((nonnull)) any better? It seems to apply
> >> to the whole function prototype rather than an individual argument
> >> though so probably not :-(
> > 
> > It's possible to specify which arguments are non-null with
> > nonnull(<arg-index>, ...).  It's harder to use, but probably more
> > Coccinelle-friendly.
> 
> Libvirt uses it, wrapped in a macro; for example:
> 
> int ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2)
> virCPUDefCopyModel(virCPUDefPtr dst,
>                    const virCPUDef *src,
>                    bool resetPolicy)
> { ...
> 
> and at least Coverity is able to use that information (libvirt had
> problems in the past where older gcc _silently_ mis-optimized a program
> that used the attribute, and ended up having our macro defined only
> during Coverity and not during normal compilation; but I think that's
> finally been resolved now that newer gcc is saner in its behavior). I
> don't know how much smarts Coccinelle has for coming up with the right
> parameter number in an automated conversion patch, though.

In the worst case, the script could have a dozen transformations, one
transformation for each possible number of function arguments.

However, I hit this Coccinelle bug when trying to implement that:
https://github.com/coccinelle/coccinelle/issues/107

-- 
Eduardo