Re: [PATCH 2/3] string: provide strscpy() and strscpy_truncate()

[Chris Metcalf]

On 05/07/2015 05:00 AM, Dan Carpenter wrote:
> On Wed, May 06, 2015 at 06:45:56PM +0200, Geert Uytterhoeven wrote:
> > On Wed, May 6, 2015 at 5:59 PM, Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:
> > > We actually do have a __must_check tag so it's easy enough to force
> > > people to check.  A different option is we could make it trigger a
> > People tend to ignore compiler warnings...
> We're doing a lot better these days with zero day build testing.  There
> is not even one ignored __must_check return in my allmodconfig.

If we keep the strscpy/strscpy_truncate distinction, I agree that having
__must_check on strscpy seems like a good idea.

> > > WARN_ONCE().
> > >
> > > #define strXcpy(dest, src, len) (({                             \
> > >          ssize_t __ret = strscpy_truncate(dest, src, len);       \
> > >          WARN_ONCE(__ret < 0, "strXcpy trancates\n");            \
> > >          __ret; }))
> > Which will probably trigger only in extreme cases in the wild, not during
> > development.
> It's less subtle than just putting an empty string there so we're more
> likely to get bug reports than with the original code.

The problem with WARN_ONCE() here is that we may be using strscpy()
to take user input of some kind.  If so, we don't want to warn if we
are truncating the string - we just want to return a suitable error up
the call stack.

--
Chris Metcalf, EZChip Semiconductor
http://www.ezchip.com

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