Re: [Qemu-devel] [libfdt][PATCH v2] implement strnlen for systems that need it

[Ian Lepore <ian@freebsd.org>]

On Sun, 2017-10-22 at 10:41 -0400, Programmingkid wrote:
> > 
> > On Oct 22, 2017, at 1:33 AM, David Gibson  wrote:
> > 
> > On Fri, Oct 20, 2017 at 04:44:58PM -0700, Richard Henderson wrote:
> > > 
> > > On 10/20/2017 10:55 AM, John Arbuckle wrote:
> > > > 
> > > > +static inline size_t strnlen(const char *string, size_t max_count)
> > > > +{
> > > > +    size_t count;
> > > > +    for (count = 0; count < max_count; count++) {
> > > > +        if (string[count] == '\0') {
> > > > +            break;
> > > > +        }
> > > > +    }
> > > > +    return count;
> > > Not to nitpick, but
> > > 
> > >  const char *p = memchr(string, 0, max_count);
> > >  return p ? max_count : p - string;
> > Richard's right, that's definitely a better implementation.
> His implementation is smaller, but this one is even smaller. Plus it uses the familiar strlen() function:
> 
> size_t strnlen(const char *string, size_t max_count)
> {
>     return strlen(string) < max_count ? strlen(string) : max_count;
> }

That is not a proper implementation of strnlen(), which is not supposed
to access any source-string bytes beyond max_count.

-- Ian