Posix Threads

Joel Sherrill joel.sherrill at OARcorp.com
Fri Feb 20 15:39:21 UTC 2004

sashti srinivasan wrote:

> Hello All,
>      I want to write my program in such a way that
> same code can be run as both rtems application and as
> a linux application.  Ofcourse, I will make small
> changes like main() instead of Init() etc.  Towards
> this end, I want to use pthread_create instead of
> rtems_task_create/start.  But the linker complains
> saying that pthread_create not found.  I searched all
> the .a files in $(prefix)/$(bsp)/lib and could not
> find pthread_create.  Please tell me how to use
> pthreads.

It sounds line you did not configure with --enable-posix
and it wasn't built.

You will have to provide an RTEMS configuration table
but otherwise, there CAN be very little difference between
the Linux and RTEMS versions of the application.

Just to help you get started, the following is a POSIX
hello world that will will run on Linux and RTEMS.  And
although Ralf doesn't like them :), I included a small
application Makefile.


#include <stdio.h>

int main(int argc, char **argv)
   printf( "hello world\n" );

  *  The following instantiates the RTEMS Configuration Information
  *  and has to be tailored for the application.

#if defined(__rtems__)
#include <rtems.h>





#include <confdefs.h>
#  Makefile

include $(RTEMS_MAKEFILE_PATH)/Makefile.inc

include $(RTEMS_CUSTOM)
include $(PROJECT_ROOT)/make/leaf.cfg

all:    hello

hello: hello.c
         $(CC_FOR_TARGET)  $(GCCSPECS) $(CPU_CFLAGS) -o hello hello.c

         rm -f *.o hello

Note that you might have to done something after the link
command to convert to a downloadable format.

>      One more doubt.  Instead of using the traditional
> makefile distributed with example applications, I have
> made my own (from whatever appeared on the console
> while running make on the distributed makefile).  This
> also works fine.  During link time, if we link with
> some .rel files, some of the directives do not work. 
> Please explain me what are these .rel files.  I am
> sorry if it is a trivial doubt.  In this case, please
> give me pointers about this.

The .rel's sound like the optional manager stubs.  If
you link against them, you will get dummy versions of
those managers which return an error for every call.

>      One help please.  I want to write a performance
> suite (similar to tmtests distributed) for rtems and
> for linux and wish to compare them.  If such an
> activity is already done, please give me pointers and
> source codes.  Also guide me if some comparative
> analysis of rtems and other OS like uClinux, RTlinux,
> eCos, RTAI etc. is reported somewhere.
> With Regards
> Srinivasan
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