Re: [Xen-devel] [PATCH v3 00/25] chardev: Convert qemu_chr_write() to take a size_t argument

[Cornelia Huck <cohuck@xxxxxxxxxx>]

On Wed, 20 Feb 2019 11:53:42 +0100
Marc-André Lureau <marcandre.lureau@xxxxxxxxxx> wrote:

> Hi
> 
> On Wed, Feb 20, 2019 at 2:02 AM Philippe Mathieu-Daudé
> <philmd@xxxxxxxxxx> wrote:
> >
> > Hi,
> >
> > This series convert the chardev::qemu_chr_write() to take unsigned
> > length argument. To do so I went through all caller and checked if
> > there are no negative value possible.  
> 
> 
> Changing signedness is problematic and can easily introduce bugs that
> are easy to miss during review.
> 
> I agree with Cornelia about idiomatic use of int. Changing "int" for
> "size_t" isn't systematically a clear win.
> 
> Even Google C++ style recommends to avoid unsigned types "(except for
> representing bitfields or modular arithmetic). Do not use an unsigned
> type merely to assert that a variable is non-negative."
> https://google.github.io/styleguide/cppguide.html#Integer_Types - see 
> rationale
> 
> Since Paolo you suggested the change, could you give some convincing
> arguments that it's worth taking the plunge?

FWIW, using an explicitly unsigned type for a length sounds fine; but
not all conversions are really convincing (albeit not wrong).

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