[Buildroot] Disabling Synopsys ARC pre-built toolchains in Buildroot

[Alexey Brodkin <Alexey.Brodkin@synopsys.com>]

Hi Thomas,

On Fri, 2015-04-17 at 21:47 +0200, Arnout Vandecappelle wrote:
> On 17/04/15 10:49, Alexey Brodkin wrote:
> >  [1] Buildroot defconfigs for uClibc are not generated by "make
> > savedefconfig" which makes it very hard to understand which options are
> > enabled and which are disabled compared to defaults.
> 
>  I think the only reason why this is the case is that uClibc didn't use to
> support savedefconfig. AFAICS 0.9.33.2 still doesn't.
> 
> 
> >  [2] Buildroot defconfig may contain options (disabled or enabled
> > compared to defaults) that might be harmful (in run-time issues like
> > performance degradation etc). Remember missing
> > UCLIBC_HAS_STRING_GENERIC_OPT. This is I think a reminder of early days
> > of Buildroot. And so blind use of Buildroot defconfig as defconfig for
> > ARC might not work well enough.
> 
>  We're certainly open to improving the BR defconfigs!

Please note that we added missing options:
 * UCLIBC_HAS_UTMP=y
 * UCLIBC_HAS_UTMPX=y
 * UCLIBC_HAS_LIBUTIL=y
 * UCLIBC_USE_NETLINK=y
 * UCLIBC_SUPPORT_AI_ADDRCONFIG=y
 * UCLIBC_HAS_LIBNSL_STUB=y

in uClibc defconfigs for ARC so the next release of ARC toolchain will have them -
https://github.com/foss-for-synopsys-dwc-arc-processors/uClibc/commit/ab87ede75f9b9b837d579c8eeef3ab4f22fd45d1

As for remaining differences between Buildroot and ARC uClibc defconfigs
these are ones I may see (comparing
https://github.com/foss-for-synopsys-dwc-arc-processors/uClibc/blob/arc-mainline-dev/extra/Configs/defconfigs/arc/defconfig with "uClibc-snapshot.config" from http://patchwork.ozlabs.org/patch/462812/):

 [1] MALLOC_GLIBC_COMPAT=y
 [2] UCLIBC_HAS_GETPT=y
 [3] UCLIBC_HAS_CTYPE_CHECKED=y
 [4] UCLIBC_HAS_HEXADECIMAL_FLOATS=y
 [5] UCLIBC_HAS_GLIBC_CUSTOM_PRINTF=y
 [6] UCLIBC_HAS_FOPEN_EXCLUSIVE_MODE=y
 [7] UCLIBC_HAS_PRINTF_M_SPEC=y
 [8] UCLIBC_HAS_SSP=y
 [9] UCLIBC_BUILD_NOW=y

Most of these options enable more compatibility with glibc or even
expand support for non-standard features like
UCLIBC_HAS_FOPEN_EXCLUSIVE_MODE.

Do you think some of them are really important and we may want to add
them in ARC defconfigs?

-Alexey