Re: [Qemu-devel] [libfdt][PATCH v3] implement strnlen for systems that need it

[Stefan Hajnoczi <stefanha@gmail.com>]

On Mon, Oct 23, 2017 at 05:27:26PM +0100, Peter Maydell wrote:
> On 23 October 2017 at 17:09, Stefan Hajnoczi <stefanha@gmail.com> wrote:
> >> +/* strnlen() is not available on Mac OS < 10.7 */
> >> +# if (MAC_OS_X_VERSION_MAX_ALLOWED < MAC_OS_X_VERSION_10_7)
> >
> > Does this cover the case where MAC_OS_X_VERSION_MAX_ALLOWED is set to
> > <1070 on a 10.7+ build machine?  It's possible that the <string.h>
> > header would define strnlen() and your code redefines the function
> > (compiler error).
> 
> In that case you don't want to use the strnlen() declaration
> from the header, you want the inline somehow, because even if
> the declaration is present and using it doesn't fail compile
> the definition won't be around at runtime.

Perhaps one way around this case is to:

# if !defined(MAC_OS_X_VERSION_10_7) || (MAC_OS_X_VERSION_MAX_ALLOWED < MAC_OS_X_VERSION_10_7)
#  include <string.h> /* make sure it isn't included again */
#  define strnlen fdt_strnlen
static inline fdt_strnlen(...) { ... }

This way the symbol strnlen() isn't used and the system headers cannot
cause problems.

Stefan