Libunwind compilation error on ARM

[LTGZZ]

Slackware ARM -current, soft-float.

../src/.libs/libunwind-arm.so: undefined reference to AO_fetch_and_add' ../src/.libs/libunwind-arm.so: undefined reference toAO_fetch_and_add1'
collect2: error: ld returned 1 exit status
make[1]: *** [Gperf-simple] Error 1
make[1]: Leaving directory `/tmp/SBo/libunwind-1.1/tests'

Have the same error with julia's libunwind.

My Make.user:

override USE_SYSTEM_LAPACK=1
override USE_SYSTEM_BLAS=1
override USE_SYSTEM_LIBGIT2=1
override USE_SYSTEM_LLVM=1
override USE_SYSTEM_FFTW=1
override USE_SYSTEM_GMP=1
override USE_SYSTEM_MPFR=1

[pao]

(identical to #13268)

[LTGZZ]

Yup, I'm sorry it was closed, I don't know why.

[pao]

You may have accidentally hit the "Close and comment" button rather than the "Comment" button. Happens all the time because they're right next to one another. You are welcome to reopen when that happens, but this is fine. Thanks.

[vtjnash]

use the system libunwind, the upstream project hasn't yet made a release that supports ARM

[LTGZZ]

I've tried the latest release and also the upstream git version of libunwind, I have the exact same problem.

[LTGZZ]

I took a look at Debian patches, but no one seemed to address the issue.
I wonder how they succeeded to compile it because I also tried under Debian and it failed...

[yuyichao]

Have you tried to use the system libunwind? (Or does the distribution you use not have a libunwind package?) Looking at the libunwind source, you could probably try to run make VERBOSE=1 to see what command libunwind uses for linking and add -latomic_ops in your LDFLAGS to see if it's just missing a library to link (and make sure you have the corresponding package installed.)

Also, I don't think ARM with soft-float is a supported target.

[yuyichao]

This seems to be the case https://github.com/archlinuxarm/PKGBUILDs/blob/034cf5528330a04cf61a711ff8175ca6b8c1cefd/extra/libunwind/PKGBUILD#L38

[tkelman]

I was fixing up libunwind's build system today and sending them patches, so if there's a good configure probe for this we can probably fix it in a less-hacky way.

[yuyichao]

I believe libunwind already have platform detection code so it's just a matter of adding the right flags.

[tkelman]

Is there some output during configure on arm that says something to the effect of "checking for atomics library: -latomic_ops" ?

[yuyichao]

In particular, it seems that it's a matter of uncommenting this

[yuyichao]

And from the archlinuxarm log, it seems that this is only needed with armv5, which actually has the vfp2 instruction set we require as an optional extension.

[ViralBShah]

Is this still a problem?

[yuyichao]

This is an upstream problem and I don't think it's fixed.