----- Original Message -----
From: "Jonathan Roelofs" <jonathan@codesourcery.com>
To: newlib@sourceware.org, "Corinna Vinschen" <vinschen@redhat.com>
Cc: "Dan Albert" <danalbert@google.com>, "JF Bastien" <jfb@chromium.org>
Sent: Wednesday, September 17, 2014 5:09:32 PM
Subject: _NEWLIB_VERSION exposure through sys/cdefs.h
Corinna,
In libc++, we'd like to be able to tell when the underlying libc is Newlib.
At
the moment, that requires us to do things like this:
#if defined(__has_include) && __has_include(<newlib.h>)
#include <newlib.h>
#endif
#if defined(_NEWLIB_VERSION)
...
#endif
The problem with that strategy is that it does not work when using gcc, as it
doesn't have __has_include support yet. It came up in discussion that
sys/cdefs.h might be the right place for that, as that's where glibc puts
__GLIBC__.
Would there be an objection to #include <newlib.h> from sys/cdefs.h? Is
there a
better way to detect Newlib that I've overlooked?
Hi Jonathan,
Corinna is on vacation until Oct 8th.
My version of glibc has __GLIBC__ defined in features.h which in glibc is
included by sys/cdefs.h.
I wouldn't have a problem with simply adding a __NEWLIB__ macro in newlib's
features.h. I also wouldn't have a real problem with including newlib.h from sys/cdefs.h
though I notice one of the newlib.h macros is missing an underscore and needs to be fixed.
A way of solving your problem now would be to look for:
#ifdef _MACHINE__DEFAULT_TYPES_H
that is set by <machine/_default_types.h> which is a newlib-specific header
that is included by sys/cdefs.h. I don't see any platform overriding sys/cdefs.h
except for x86-linux and it eventually includes <machine/_default_types.h> as
well.
Regards,
-- Jeff J.