powerpc-rtems-gcc question (fwd)

joel at oarcorp.com joel at oarcorp.com
Fri Oct 30 15:02:49 UTC 1998

---------- Forwarded message ----------
Date: Thu, 29 Oct 1998 19:44:23 -0600 (CST)
From: joel at OARcorp.com
To: Brendan Simon <brendan at dgs.monash.edu.au>
Cc: rtems-list <rtems-list at oarcorp.com>
Subject: Re: powerpc-rtems-gcc question

On Sat, 31 Oct 1998, Brendan Simon wrote:

> I have successfully compiled the gcc suite following the rtems-4.0.0
> documentation.  Before I try to use RTEMS I thought I would try a little
> test that flashes a led on the ADS board.  It is about 20 lines of code
> but the executalbe seems quite large.  I used objcopy to generate an
> s-record and it is nearly 4kb.  I am not using any libc functions (that
> I know of anyway).  Is the compliler linking in all of libc or parts of
> RTEMS by default ???

If it is only 4K, then it is unlikely you are getting much of anything
other than crt0 and a C routine.  Use powerpc-rtems-nm to see the symbols
in it.  Srecords also use 2 ascii bytes to represent 1 byte in the real
image plus per record overhead.  So your real image size is under 2K.

> Can I use this as a pure powerpc compiler without an implicit linking.
> It also complains about _start not being defined.  I assume crt0.o is
> being linked in but I'm not quite sure which one and where the source is
> that generated the crt0.o

The answer is yes.  Look at the gcc options like -nostdlib and
-nostdinclude or something like that.  

> The command is
> powerpc-rtems-gcc -Wall -O2 -Wl,-Ttext=0x1000000,-Tdata=0x20000000 -o
> leds.elf leds.c
> The only library that I assume is being linked in implicitly is libc.a.
> Is this true ?

Probably.  Adding a -v will check that out by printing the ld command.

> Are there any linker scripts involved.  Can I define my own if need be
> and where should I put it.

See the ld line with the -v option to check it out for sure.

Joel Sherrill                    Director of Research & Development
joel at OARcorp.com                 On-Line Applications Research
Ask me about RTEMS: a free RTOS  Huntsville AL 35805
   Support Available             (256) 722-9985

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