Re: Building newlib and gcc for ARM Thumb2

[Jeff Johnston <jjohnstn at redhat dot com>]

Regarding building newlib, you should know about multilibs.  Multilibs 
are versions of the library
built with specific options.  The compiler determines what multilibs 
should exist and how to build them. 

The compiler has an option: --print-multi-lib which specifies the 
various permutations
of options to build the library with and what subdirectories to put them 
under.  Newlib issues this
option to determine how many multilibs to build and how to do it.

For example, the mn10300-elf-gcc compiler I have on my system gives:

[jjohnstn@vermillion]$ ./mn10300-elf-gcc --print-multi-lib
.;
am33;@mam33
am33-2;@mam33-2
am34;@mam34

Note that this indicates there are 3 additional multilibs in addition to 
the default library (.;).  The
am33 version of the library uses a subdirectory named "am33" and is 
compiled with the -mam33 option, the am33-2 is built with -mam33-2, 
etc...  Sometimes you have permutations and can end up with nested 
subdirectories (e.g. a bigendian and soft-float library could be stored 
under a subdirectory be/sf).

When you compile/link an application via gcc and specify a particular 
multilib option, the compiler will try and
find the library under the specified subdirectory or subdirectories of 
the location where newlib has been specified to be.  This does not occur 
if you do the link yourself via ld (you have to figure out where the 
library has been stored).

So, check to see if the compiler you are ultimately using in the newlib 
build has a thumb2 multilib and the option(s) used (via 
--print-multi-lib).  Then, verify that the compiler is setting the 
__thumb2__ flag when this particular option is chosen which is what 
ultimately determines if the thumb2-specific code in setjmp.S is being 
activated properly.

-- Jeff J.

Rob Emanuele wrote:
> Alexandre,
>
> Yes, it builds but I don't see any code generated for thumb2.  I see
> ARM and thumb but not thumb2.
>
> --Rob
>
>
> On Tue, Feb 3, 2009 at 9:14 AM, Alexandre Pereira Nunes
> <alexandre.nunes@gmail.com> wrote:
>   
> > On Sun, Feb 1, 2009 at 4:52 PM, Rob Emanuele <poorarm@shoreis.com> wrote:
> >     
> > > Greetings,
> > >
> > > I'm trying to build newlib and gcc for a Cortex-M3 processor.  What
> > > are the best ways for doing this?  I'm running into a problem with the
> > > "setjmp" call as it is not being compiled correctly for Thumb2.  It is
> > > only being compiled for Thumb.  Are there a set of instructions on the
> > > proper build procedure to get all the libs built for arm, thumb, and
> > > thumb2?
> > >
> > > Thanks,
> > >
> > > Rob Emanuele
> > >
> > >       
> > Are you trying 1.17.0 ? It should build fine.
> >
> >