Re: [Qemu-devel] [PATCH 03/14] disas/arm-a64.cc: Include osdep.h first

[Peter Maydell <peter.maydell@linaro.org>]

On 9 February 2016 at 15:25, Peter Maydell <peter.maydell@linaro.org> wrote:
> Rearrange include directives so that we include osdep.h first.
> This has to be done manually because clean-includes doesn't
> handle C++.
>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  disas/arm-a64.cc | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/disas/arm-a64.cc b/disas/arm-a64.cc
> index d4d46d5..9280950 100644
> --- a/disas/arm-a64.cc
> +++ b/disas/arm-a64.cc
> @@ -17,12 +17,13 @@
>   * along with this program.  If not, see <http://www.gnu.org/licenses/>.
>   */
>
> -#include "vixl/a64/disasm-a64.h"
> -
>  extern "C" {
> +#include "qemu/osdep.h"
>  #include "disas/bfd.h"
>  }
>
> +#include "vixl/a64/disasm-a64.h"
> +
>  using namespace vixl;
>
>  static Decoder *vixl_decoder = NULL;

So this patch doesn't build on the old mingw32 compiler. I think this
is because this compiler is not C++11, and so its <stdint.h> doesn't
provide various macros for C++ unless __STDC_CONSTANT_MACROS,
__STDC_LIMIT_MACROS and __STDC_FORMAT_MACROS are defined before the
first inclusion of <stdint.h>.

libvixl's globals.h defines these constants, but this only works if
globals.h is first-include, so making osdep.h first-include then
results in stdint.h being included before globals.h has a chance
to set the defines.

What's the best way to deal with this? I can see a couple of options:

(1) as a special case, for this file include disasm-a64.h before
osdep.h
(2) as a special case, for this file manually define the __STDC_*
before including osdep.h
(3) make osdep.h itself define the __STDC_* constants so it works
with C++-before-C++11 as well as with C and with C++11

I think I prefer (3) (though it does mean we will have to tweak
osdep.h in future if a new vixl version should ever require any
further similar #defines.)

thanks
-- PMM