[lldb-dev] Pre-processor definition confusion

[Zachary Turner]

Is there any value in having an LLDB_HOST_XXX set of macros such as the
following:

LLDB_HOST_APPLE
LLDB_HOST_WIN32
LLDB_HOST_MINGW
LLDB_HOST_LINUX
LLDB_HOST_BSD

The last one would translate to __FreeBSD__ || __FreeBSD_kernel__ ||
__OpenBSD__ || __NetBSD__

In lldb/Host/Config.h, we use the presence of any of these 4 things to
include lldb/Host/freebsd/Config.h.  But then in most other places, we
either only check for __FreeBSD__ or only check for __FreeBSD_kernel__.
 Since the platforms are similar, it seems like *most of the time* you just
want to check for all 4, and checking for some subset of those would be the
exception.

For example, in my previous HostThread refactoring changelist, I created
this HostThreadFreeBSD class.  That class isn't going to be compiled on
OpenBSD or NetBSD though (at least on the CMake build, which I know you
don't use, but still).  So that seems like a bug.  Do you agree that more
often than not, when we check for FreeBSD we want to check for all of the
BSD variants?  Or am I wrong there?

On Fri, Sep 12, 2014 at 10:14 AM, Ed Maste <emaste at freebsd.org> wrote:

> On 12 September 2014 12:59, Zachary Turner <zturner at google.com> wrote:
> > The important thing seems to be whether glibc implies linux, not the
> other
> > way around.
>
> It doesn't -- Debian k/FreeBSD has __GLIBC__ and __FreeBSD_kernel__,
> and not __linux__.
>
> > The issue is that all of our CMake decisions are based on OS platform.
> If I
> > want to conditionally compile an entire file based on one of these
> > conditions, I need to translate it into something that fits well into the
> > CMake build.
>
> That should be fine, although in some cases there won't be a mapping
> to a single OS if multiple macros are used.
>
> An OS to macro map would include, for example:
>
> FreeBSD: __FreeBSD__, __FreeBSD_kernel__
> Linux distros: __linux__, __GLIBC__
> kFreeBSD: __GLIBC__, __FreeBSD_kernel__
>
> The kFreeBSD project needs to use the FreeBSD kernel's debugging
> interface (e.g., the ptrace syscall and constants) and glibc's
> userland interfaces (e.g., setting thread names).
>
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