Re: [Qemu-devel] [PATCH v2 0/3] Fix strncpy() warnings for GCC8 new -Wstringop-truncation

[Daniel P . Berrangé]

On Tue, Dec 18, 2018 at 12:03:34PM -0500, Michael S. Tsirkin wrote:
> On Tue, Dec 18, 2018 at 05:38:17PM +0100, Paolo Bonzini wrote:
> > On 18/12/18 15:54, Michael S. Tsirkin wrote:
> > > On Tue, Dec 18, 2018 at 03:45:08PM +0100, Paolo Bonzini wrote:
> > >> On 18/12/18 15:31, Michael S. Tsirkin wrote:
> > >>> Do you happen to know why does it build fine with
> > >>> Gcc 8.2.1?
> > >>>
> > >>> Reading the GCC manual it seems that
> > >>> there is a "nostring" attribute that means
> > >>> "might not be 0 terminated".
> > >>> I think we should switch to that which fixes the warning
> > >>> but also warns if someone tries to misuse these
> > >>> as C-strings.
> > >>>
> > >>> Seems to be a better option, does it not?
> > >>>
> > >>>
> > >>
> > >> Using strpadcpy is clever and self-documenting, though.  We have it
> > >> already, so why not use it.
> > >>
> > >> Paolo
> > > 
> > > The advantage of nonstring is that it will catch attempts to
> > > use these fields with functions that expect a 0 terminated string.
> > > 
> > > strpadcpy will instead just silence the warning.
> > 
> > Ah, I see.  We could also do both, that's a matter of taste.
> > 
> > Paolo
> 
> Do you happen to know how to make gcc check the buffer size
> for strpadcpy? Is the name strncpy just hard-coded?

GCC provides  strncpy as a builtin function and its warning only
checks its builtin.

Regards,
Daniel
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