That's Legal?!

Today I found this gem on the GIT mailing list:

Timo Hirvonen  wrote:
> Linus Torvalds  wrote:
>
> > +void verify_filename(const char *prefix, const char *arg)
> > +{
> > +   const char *name;
> > +   struct stat st;
> > +
> > +   if (*arg == '-')
> > +       die("bad flag '%s' used after filename", arg);
> > +   name = prefix ? prefix_filename(prefix, strlen(prefix), arg) : arg;
> > +   if (!lstat(name, &st))
> > +       return;
> > +   if (errno == ENOENT);
>
> Extra semicolon.

Just what were the authors of C thinking when they decided to allow:

  if (errno == ENOENT);

as a legal statement? It clearly has no real purpose as the "then-clause" of the if statement is completely empty.

What's really bad is this language feature is also available in C++, Objective-C, Java, Perl, etc. I'm so glad modern language designers have kept the warts intact.