libunwind

This is version 1.4 of the unwind library. This library supports several architecture/operating-system combinations:

System	Architecture	Status
Linux	x86-64	✓
Linux	x86	✓
Linux	ARM	✓
Linux	AArch64	✓
Linux	PPC64	✓
Linux	SuperH	✓
Linux	IA-64	✓
Linux	PARISC	Works well, but C library missing unwind-info
Linux	Tilegx	64-bit mode only
Linux	MIPS	Newly added
HP-UX	IA-64	Mostly works, but known to have serious limitations
FreeBSD	x86-64	✓
FreeBSD	x86	✓
FreeBSD	AArch64	✓
Solaris	x86-64	✓

Libc Requirements

libunwind depends on getcontext(), setcontext() functions which are missing from C libraries like musl-libc because they are considered to be "obsolescent" API by POSIX document. The following table tries to track current status of such dependencies

• r, requires
• p, provides its own implementation
• empty, no requirement

Archtecture	getcontext	setcontext
aarch64	p
arm	p
hppa	p	p
ia64	p	r
mips	p
ppc32	r
ppc64	r	r
s390x	p	p
sh	r
tilegx	r	r
x86	p	r
x86_64	p	p

General Build Instructions

In general, this library can be built and installed with the following commands:

$ ./autogen.sh # Needed only for building from git. Depends on libtool.
$ ./configure
$ make
$ make install prefix=PREFIX

where PREFIX is the installation prefix. By default, a prefix of /usr/local is used, such that libunwind.a is installed in /usr/local/lib and unwind.h is installed in /usr/local/include. For testing, you may want to use a prefix of /usr/local instead.

Building with Intel compiler

Version 8 and later

Starting with version 8, the preferred name for the IA-64 Intel compiler is icc (same name as on x86). Thus, the configure-line should look like this:

$ ./configure CC=icc CFLAGS="-g -O3 -ip" CXX=icc CCAS=gcc CCASFLAGS=-g \
    LDFLAGS="-L$PWD/src/.libs"

Building on HP-UX

For the time being, libunwind must be built with GCC on HP-UX.

libunwind should be configured and installed on HP-UX like this:

$ ./configure CFLAGS="-g -O2 -mlp64" CXXFLAGS="-g -O2 -mlp64"

Caveat: Unwinding of 32-bit (ILP32) binaries is not supported at the moment.

Workaround for older versions of GCC

GCC v3.0 and GCC v3.2 ship with a bad version of sys/types.h. The workaround is to issue the following commands before running configure:

$ mkdir $top_dir/include/sys
$ cp /usr/include/sys/types.h $top_dir/include/sys

GCC v3.3.2 or later have been fixed and do not require this workaround.

Building for PowerPC64 / Linux

For building for power64 you should use:

$ ./configure CFLAGS="-g -O2 -m64" CXXFLAGS="-g -O2 -m64"

If your power support altivec registers:

$ ./configure CFLAGS="-g -O2 -m64 -maltivec" CXXFLAGS="-g -O2 -m64 -maltivec"

To check if your processor has support for vector registers (altivec):

cat /proc/cpuinfo | grep altivec

and should have something like this:

cpu             : PPC970, altivec supported

If libunwind seems to not work (backtracing failing), try to compile it with -O0, without optimizations. There are some compiler problems depending on the version of your gcc.

Building on FreeBSD

General building instructions apply. To build and execute several tests on older versions of FreeBSD, you need libexecinfo library available in ports as devel/libexecinfo. This port has been removed as of 2017 and is indeed no longer needed.

Regression Testing

After building the library, you can run a set of regression tests with:

$ make check

Expected results on IA-64 Linux

Unless you have a very recent C library and compiler installed, it is currently expected to have the following tests fail on IA-64 Linux:

• Gtest-init (should pass starting with glibc-2.3.x/gcc-3.4)
• Ltest-init (should pass starting with glibc-2.3.x/gcc-3.4)
• test-ptrace (should pass starting with glibc-2.3.x/gcc-3.4)
• run-ia64-test-dyn1 (should pass starting with glibc-2.3.x)

This does not mean that libunwind cannot be used with older compilers or C libraries, it just means that for certain corner cases, unwinding will fail. Since they're corner cases, it is not likely for applications to trigger them.

Note: If you get lots of errors in Gia64-test-nat and Lia64-test-nat, it's almost certainly a sign of an old assembler. The GNU assembler used to encode previous-stack-pointer-relative offsets incorrectly. This bug was fixed on 21-Sep-2004 so any later assembler will be fine.

Expected results on x86 Linux

The following tests are expected to fail on x86 Linux:

• test-ptrace

Expected results on x86-64 Linux

The following tests are expected to fail on x86-64 Linux:

• run-ptrace-misc (see http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18748 and http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18749)

Expected results on PARISC Linux

Caveat: GCC v3.4 or newer is needed on PA-RISC Linux. Earlier versions of the compiler failed to generate the exception-handling program header (GNU_EH_FRAME) needed for unwinding.

The following tests are expected to fail on x86-64 Linux:

• Gtest-bt (backtrace truncated at kill() due to lack of unwind-info)
• Ltest-bt (likewise)
• Gtest-resume-sig (Gresume.c:my_rt_sigreturn() is wrong somehow)
• Ltest-resume-sig (likewise)
• Gtest-init (likewise)
• Ltest-init (likewise)
• Gtest-dyn1 (no dynamic unwind info support yet)
• Ltest-dyn1 (no dynamic unwind info support yet)
• test-setjmp (longjmp() not implemented yet)
• run-check-namespace (toolchain doesn't support HIDDEN yet)

Expected results on HP-UX

make check is currently unsupported for HP-UX. You can try to run it, but most tests will fail (and some may fail to terminate). The only test programs that are known to work at this time are:

• tests/bt
• tests/Gperf-simple
• tests/test-proc-info
• tests/test-static-link
• tests/Gtest-init
• tests/Ltest-init
• tests/Gtest-resume-sig
• tests/Ltest-resume-sig

Expected results on PPC64 Linux

make check should run with no more than 10 out of 24 tests failed.

Expected results on Solaris x86-64

make check is passing 27 out of 33 tests. The following six tests are consistently failing:

• Gtest-concurrent
• Ltest-concurrent
• Ltest-init-local-signal
• Lrs-race
• test-setjmp
• x64-unwind-badjmp-signal-frame

Performance Testing

This distribution includes a few simple performance tests which give some idea of the basic cost of various libunwind operations. After building the library, you can run these tests with the following commands:

$ cd tests
$ make perf

Contacting the Developers

Please direct all questions regarding this library to [email protected].

You can do this by sending an email to [email protected] with a body of "subscribe libunwind-devel", or you can subscribe and manage your subscription via the web-interface at https://savannah.nongnu.org/mail/?group=libunwind.

You can also interact on our GitHub page: https://github.com/libunwind/libunwind.