Building uclibc for big-endian and little-endian target.

[Mike Frysinger]

On Wednesday 16 October 2013 12:13:12 Sedat Dilek wrote:
> On Wed, Oct 16, 2013 at 5:23 PM, Mike Frysinger <vapier at gentoo.org> wrote:
> > On Wednesday 16 October 2013 04:23:17 Sedat Dilek wrote:
> >> On Wed, Oct 16, 2013 at 9:04 AM, Mike Frysinger wrote:
> >> > On Tuesday 15 October 2013 15:00:40 Khem Raj wrote:
> >> >> On Oct 15, 2013, at 10:30 AM, Steve Ellcey wrote:
> >> >> > I have a question about endiness and uclibc.  I am trying to build
> >> >> > multiple versions of uclibc for MIPS, including big and little
> >> >> > endian versions.  What I notice is that in Rules.mak there are
> >> >> > lines:
> >> >> > 
> >> >> > CPU_LDFLAGS-$(ARCH_LITTLE_ENDIAN) += -Wl,-EL
> >> >> > CPU_LDFLAGS-$(ARCH_BIG_ENDIAN)    += -Wl,-EB
> >> >> > 
> >> >> > to add -EL or -EB to linker commands (this seems to be generic for
> >> >> > all architectures).
> >> >> > 
> >> >> > What I do not see is any generic (or MIPS specific) code to add -EL
> >> >> > or -EB to CPU_CFLAGS (or CPU_FLAGS-y to be exact).  I am wondering
> >> >> > if there is a specific reason for this?  Right now the uclibc
> >> >> > build seems to assume that the compiler I am using to build uclibc
> >> >> > will always generate the correct endiness without any flags.
> >> >> 
> >> >> That was consensus we had some time ago. Otherwise these flags were
> >> >> getting too many and difficult to deal with.
> >> > 
> >> > well, i think that was more focused on cpu/arch/tune flags.  we still
> >> > have endian flags in there for various targets.  adding the right
> >> > logic for mips would be OK imo.
> >> 
> >> As the Freetz router project had to deal with BE/LE issues, we (yes, I
> >> 
> >> was more active these days) decided to define the Kconfig logic in:
> >>      extra/Configs/Config.mips
> >> 
> >> ...and added the the CPU_FLAGS-* (CPU optimization etc.) stuff to...
> >> 
> >>      Rules.mak
> >> 
> >> Please see the patch in [1] for more details.
> > 
> > that patch is exactly the sort of thing we are not adding more support
> > for
> 
> what had you in mind, how would you realize it?

as Khem said, if you want to target a specific cpu (-march/-mtune/etc...), then 
update UCLIBC_EXTRA_CFLAGS accordingly.  there's really no difference between a 
Kconfig option with hardcoded cpu name and the user adding the same name to the 
cflags.  except the kconfig list is a constantly losing route.
-mike
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