Re: [ARM] EABI and the default to short enums

[Sebastian Huber <sebastian dot huber at embedded-brains dot de>]

On 02/14/2012 04:05 PM, Ian Lance Taylor wrote:
> Sebastian Huber<sebastian.huber@embedded-brains.de>  writes:
>
> > the default ARM EABI configuration uses short enums by default (from
> > "gcc/config/arm/arm.c":
> >
> > /* AAPCS based ABIs use short enums by default.  */
> >
> > static bool
> > arm_default_short_enums (void)
> > {
> >    return TARGET_AAPCS_BASED&&  arm_abi != ARM_ABI_AAPCS_LINUX;
> > }
> >
> > This causes a major headache for me since some libraries assume that
> > sizeof(any enum)>  1, e.g. the standard XDR library.  Is the only
> > possible way to disable short enums to set the ABI to
> > ARM_ABI_AAPCS_LINUX?  Which side effects does this have?
>
> This question would be better asked on the mailing list
> gcc-help@gcc.gnu.org rather than gcc@gcc.gnu.org.  The gcc@ mailing list
> is for issues related to the development of gcc itself.  Please take any
> followups to gcc-help.  Thanks.
>
> You can use -fno-short-enums.  However, see the note about ABI
> compatibility in the -fshort-enums doc.

The problem is that I need a proper GCC ARM configuration for the RTEMS tool 
chain.  To do this I have to provide the right definitions in

gcc/config/arm/rtems-eabi.h
gcc/config/arm/t-rtems-eabi

and this is clearly not a GCC user problem.  The so called ARM ELF 
configuration didn't use short enums by default.  It seems that Linux faced 
this problem before and now we have this exception in the 
arm_default_short_enums() function above.  I want to preserve the ARM ELF 
behavior with respect to enums also in the ARM EABI configuration.  The 
question is now who to achieve this.  One option is to set the ABI to 
ARM_ABI_AAPCS_LINUX also for the RTEMS tool chain, but I am not sure that this 
is the right thing.

--
Sebastian Huber, embedded brains GmbH

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