#includes and #defined

[Warner Losh]

On Thu, Aug 9, 2018 at 11:51 PM, Erich Dollansky <
freebsd.ed.lists at sumeritec.com> wrote:

> Hi,
>
> On Fri, 10 Aug 2018 12:40:48 +0800
> blubee blubeeme <gurenchan at gmail.com> wrote:
>
> > On Fri, Aug 10, 2018 at 8:28 AM Erich Dollansky <
> > freebsd.ed.lists at sumeritec.com> wrote:
> >
> > > Hi,
> > >
> > > On Fri, 10 Aug 2018 08:01:42 +0800
> > > blubee blubeeme <gurenchan at gmail.com> wrote:
> > >
> > > > What's the proper way to define and include FreeBSD amd64 in GNU
> > > > Makefiles
> > > >
> > > > Do we define FreeBSD as x86_64 or amd64 also is it __FreeBSD__,
> > > > FreeBSD__, or __FreeBSD
> > > >
> > > > I've seen all of the above looking through different projects.
> > >
> > > clang defines '__FreeBSD__'
> > >
> > > Erich
> > >
> >
> > What about the architecture name is it recommended to use x86_64 or
> > amd64?
>
> my clang reports on an Intel CPU:
>
> #define __amd64 1
> #define __amd64__ 1
> #define __x86_64 1
> #define __x86_64__ 1
>
> as defined.
>
> It reports
>
> #define __aarch64__ 1
>
> on an 64 bit ARM CPU.
>

'man 7 arch' will tell you these things:

           amd64              __amd64__, __x86_64__

it contains the preferred list of macros to use. Ideally, you'd use the
first one listed, though all the ones listed are supported. Others might
not be.

Warner