ARM unwind issue

ARM unwind issue

[Andre Renaud]

Hi,
I'm trying to build some software using musl on an ARM platform, and
am getting the following error:
arm-none-linux-gnueabi-gcc
-specs=/home/andre/work/package-builder/staging/lib/musl-gcc.specs -o
program program.o
/tools/arm/arm-2010q1/bin/../lib/gcc/arm-none-linux-gnueabi/4.4.1/../../../../arm-none-linux-gnueabi/bin/ld:
program: hidden symbol `__aeabi_unwind_cpp_pr0' in
/tools/arm/arm-2010q1/bin/../lib/gcc/arm-none-linux-gnueabi/4.4.1/libgcc_eh.a(unwind-arm.o)
is referenced by DSO

Any ideas on what I've messed up in either my musl build, or my
cflags/lflags to cause this?

Regards,
Andre

Re: ARM unwind issue

[Rich Felker]

On Tue, Jan 29, 2013 at 12:02:37PM +1300, Andre Renaud wrote:
> Hi,
> I'm trying to build some software using musl on an ARM platform, and
> am getting the following error:
> arm-none-linux-gnueabi-gcc
> -specs=/home/andre/work/package-builder/staging/lib/musl-gcc.specs -o
> program program.o
> /tools/arm/arm-2010q1/bin/../lib/gcc/arm-none-linux-gnueabi/4.4.1/../../../../arm-none-linux-gnueabi/bin/ld:
> program: hidden symbol `__aeabi_unwind_cpp_pr0' in
> /tools/arm/arm-2010q1/bin/../lib/gcc/arm-none-linux-gnueabi/4.4.1/libgcc_eh.a(unwind-arm.o)
> is referenced by DSO
> 
> Any ideas on what I've messed up in either my musl build, or my
> cflags/lflags to cause this?

musl itself does not use any unwinding facilities. However, on ARM, at
least with some gcc versions, some arithmetic functions in libgcc.a
are pulling in exception stuff for no good reason. I believe this is a
bug in the CFLAGS gcc is using to build libgcc, rather than an
intentional bad behavior, but I haven't looked into it in depth.

With that said, it looks like the problem is that, when musl libc.so
was built, it contained references to __aeabi_unwind_cpp_pr0 (from
libgcc.a) which were not resolved. Normally musl's configure script
also includes -lgcc_eh in $(LIBCC) for precisely this reason, so the
first thing I would do is check your config.mak and see what configure
chose for $(LIBCC).

If you figure out what went wrong, please report it to the list so we
can try to avoid the same thing happening for other users.

Rich

Re: ARM unwind issue

[Isaac Dunham]

On Tue, 29 Jan 2013 12:02:37 +1300
Andre Renaud <andre@bluewatersys.com> wrote:

> Hi,
> I'm trying to build some software using musl on an ARM platform, and
> am getting the following error:
> arm-none-linux-gnueabi-gcc
> -specs=/home/andre/work/package-builder/staging/lib/musl-gcc.specs -o
> program program.o
> /tools/arm/arm-2010q1/bin/../lib/gcc/arm-none-linux-gnueabi/4.4.1/../../../../arm-none-linux-gnueabi/bin/ld:
> program: hidden symbol `__aeabi_unwind_cpp_pr0' in
> /tools/arm/arm-2010q1/bin/../lib/gcc/arm-none-linux-gnueabi/4.4.1/libgcc_eh.a(unwind-arm.o)
> is referenced by DSO

A few details that might be informative:

1: I'm guessing that this is a prepackaged glibc-targetted x86->armel cross toolchain from Linaro, specifically their 2010 release?

2: I guess you're manually duplicating 
REALGCC=/tools/arm/arm-2010q1/bin/gcc musl-gcc program.c -o program.o

3: Does this occur even with a trivial program (hello world or 
int main(){ }) ?

> Any ideas on what I've messed up in either my musl build, or my
> cflags/lflags to cause this?

Googling "hidden symbol is referenced by DSO" I find that similar problems occurr with newlib when not linked with libgcc.
So it would probably help figure it out if you attached your config.mak and musl-gcc.specs.


> Regards,
> Andre

-- 
Isaac Dunham <idunham@lavabit.com>

Re: ARM unwind issue

[Andre Renaud]

>> I'm trying to build some software using musl on an ARM platform, and
>> am getting the following error:
>> arm-none-linux-gnueabi-gcc
>> -specs=/home/andre/work/package-builder/staging/lib/musl-gcc.specs -o
>> program program.o
>> /tools/arm/arm-2010q1/bin/../lib/gcc/arm-none-linux-gnueabi/4.4.1/../../../../arm-none-linux-gnueabi/bin/ld:
>> program: hidden symbol `__aeabi_unwind_cpp_pr0' in
>> /tools/arm/arm-2010q1/bin/../lib/gcc/arm-none-linux-gnueabi/4.4.1/libgcc_eh.a(unwind-arm.o)
>> is referenced by DSO
>
> A few details that might be informative:
>
> 1: I'm guessing that this is a prepackaged glibc-targetted x86->armel cross toolchain from Linaro, specifically their 2010 release?

It's the codesourcery 2010q1 release.

> 2: I guess you're manually duplicating
> REALGCC=/tools/arm/arm-2010q1/bin/gcc musl-gcc program.c -o program.o
I actually wasn't using musl-gcc, I was manually adding the '-spec' line.

It turns out that the root cause was a mistake on my behalf when
configuring musl, which resulted in LIBCC not being set properly in
config.mak.

Regards,
Andre

Re: ARM unwind issue

[Rich Felker]

On Wed, Jan 30, 2013 at 08:56:27AM +1300, Andre Renaud wrote:
> > 2: I guess you're manually duplicating
> > REALGCC=/tools/arm/arm-2010q1/bin/gcc musl-gcc program.c -o program.o
> I actually wasn't using musl-gcc, I was manually adding the '-spec' line.
> 
> It turns out that the root cause was a mistake on my behalf when
> configuring musl, which resulted in LIBCC not being set properly in
> config.mak.

Yes, that would do it. BTW, note that musl is _not_ using libgcc_eh
for anything itself. The need for libgcc_eh is due to libgcc having
unwanted dependencies on it, and musl needing those parts of libgcc.

Rich