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

[Eric Blake]

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.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

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