[Xenomai] xenomai 2 LDFLAGS wrappers, posix only

Henning Schild henning.schild at siemens.com
Wed Jan 11 15:47:59 CET 2017

Am Wed, 11 Jan 2017 12:03:23 +0100
schrieb Philippe Gerum <rpm at xenomai.org>:

> On 01/10/2017 04:07 PM, Henning Schild wrote:
> > Hi,
> > 
> > i am about to include three more wrappers into xenomai2 to
> > assert_nrt, later i plan to create a xenomai3 patch as well. The
> > functions to wrap are __cxa_guard_(acquire|release|abort). They
> > contain mutexes protecting the initialization state of static
> > objects in c++ code, often found when people implement the
> > singleton pattern.
> > 
> > I have got the wrapping code but found that xeno-config will create
> > the wrapping LDFLAGS only for the posix skin. Is that intentional
> > or an inconsistency?
> > Even the wrappers in the "common" skin get applied for posix only.
> > 
> > I tried calling malloc/free in a "--skin=native" example and did not
> > get the SIGXCPU.
> > 
> > Now i am guessing that the way wrappers are applied in xenomai2 is
> > somehow inconsistent. Is that something that should be fixed by
> > having common and per skin wrappers, or would it be ok to simply
> > always append the posix LDFLAGS as well?  
> --posix is supposed to be passed only when a wrapping is expected.
> Omitting it allows to build apps over non-POSIX Xenomai APIs, while
> assuming that any POSIX call also present in the code can only be
> obtained from the glibc.

Ok i see. Just adding the --posix all the time would change the
implementation of all the pthread_* stuff where the developer might
just want to use non-rt pthreads.

There seem to be two classes of wrappers. Those that just assert_nrt()
and do not change the implementation of the function to be called. And
the other class actually replaces the original implementation.

The ones that just insert the assert_nrt() are relevant for all skins
and should be applied there, while at the moment they are only used for

For xenomai3 that is malloc and free (./lib/cobalt/assert_context.c),
for xenomai2 it is those two plus gettimeofday
(src/skins/common/assert_context.c). These should be wrapped in any
skin, not just posix.

The three __cxa_guard wrappers would also be of the "insert assertion"
type and should therefore go into all skins.


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