gcc for ARM in thumb mode

gcc for ARM in thumb mode

[Dmytro Bablinyuk]

I am trying to figure out whether it's possible at all to build a gcc 
cross-compiler for ARM720T in thumb mode? I am looking, if possible, to 
use uClibc.
Does anyone has any experience with this?
I have gcc 2.95.3(with uClibc) configured and running for 
target=arm-linux perfectly. Do I just need to change the target or some 
more work required?

Thank you,

Re: gcc for ARM in thumb mode

[Richard Earnshaw]

> I am trying to figure out whether it's possible at all to build a gcc 
> cross-compiler for ARM720T in thumb mode? I am looking, if possible, to 
> use uClibc.
> Does anyone has any experience with this?
> I have gcc 2.95.3(with uClibc) configured and running for 
> target=arm-linux perfectly. Do I just need to change the target or some 
> more work required?
> 
> Thank you,
> 

Gcc already contains support for compiling to thumb; just add -mthumb to 
all your compiles and you will get thumb code generated.

Whether the rest of the arm-linux tools can cope with this is a separate 
issue.

R.

RE: gcc for ARM in thumb mode

[Dave Murphy]

aha, somone who might know.

Apologies if this is a can of worms :)

Is it possible to link ADS/SDT compiled libraries using an arm targetted
gcc?

gcc currently complains about the EABI version number being different. Is
there any significant difference in the elf files between the compiler
toolchains?

I did some searches for info

it appears that there is/was a collision with the EF_ARM_SYMSARESORTED and
EF_INTERWORK flags from EABI 0 is this still the case?

I can't seem to find any information on interworking. Has this been
deprecated in favour of some other method of calling between ARM and thumb
code?

Dave

> -----Original Message-----
> From: gcc-owner@gcc.gnu.org [mailto:gcc-owner@gcc.gnu.org]On Behalf Of
> Richard Earnshaw
> Sent: 20 February 2003 10:43
> To: Dmytro Bablinyuk
> Cc: gcc@gnu.org; Richard.Earnshaw@arm.com
> Subject: Re: gcc for ARM in thumb mode

> Gcc already contains support for compiling to thumb; just add -mthumb to
> all your compiles and you will get thumb code generated.
>
> Whether the rest of the arm-linux tools can cope with this is a separate
> issue.
>
> R.
>
>

Re: gcc for ARM in thumb mode

[Richard Earnshaw]

> aha, somone who might know.
> 
> Apologies if this is a can of worms :)

Very wriggly ones ;-)

> 
> Is it possible to link ADS/SDT compiled libraries using an arm targetted
> gcc?

In summary no.  GCC and ADS do not use the same procedure call standard, 
so while you might "get away with it", the chances are that something will 
come along quietly and bite you when you are least expecting it (the 
differences are largely in the corners, but they do exist and some of the 
corners have plenty of dust).

Note that ADS and SDT don't share a common ABI either (though you might be 
able to persuade the ADS compiler to generate SDT confoming code -- I've 
never tried it).

> 
> gcc currently complains about the EABI version number being different. Is
> there any significant difference in the elf files between the compiler
> toolchains?

To be pedantic, gcc isn't complaining, but the GNU linker is.  Objects 
created by ADS are marked differently to those created by GCC/GAS.

> 
> I did some searches for info
> 
> it appears that there is/was a collision with the EF_ARM_SYMSARESORTED and
> EF_INTERWORK flags from EABI 0 is this still the case?

Don't know the answer to that one, sorry.

> I can't seem to find any information on interworking. Has this been
> deprecated in favour of some other method of calling between ARM and thumb
> code?

GCC's interworking code has been tested even less thoroughly than just 
plain thumb code (which is to say it hasn't had much testing at all).

That all sounds a bit negative.  The best encouragement I can give is that 
ARM is currently working on a new and far more tightly laid down EABI 
standard; this will be taking the Generic C++ ABI as the base for C++ 
code.  Once this work is complete it would be nice to see configurations 
of GCC conforming to it.

R.