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# libunwind
[](https://travis-ci.org/libunwind/libunwind)
This library supports several architecture/operating-system combinations:
| System | Architecture | Status |
| :------ | :----------- | :----- |
| Linux | x86-64 | ✓ |
| Linux | x86 | ✓ |
| Linux | ARM | ✓ |
| Linux | AArch64 | ✓ |
| Linux | PPC32 | ✓ |
| 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 |
| Linux | RISC-V | 64-bit only |
| 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
| Architecture | getcontext | setcontext |
|--------------|------------|------------|
| aarch64 | p | |
| arm | p | |
| hppa | p | p |
| ia64 | p | r |
| mips | p | |
| ppc32 | r | |
| ppc64 | r | r |
| riscv | p | p |
| 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:
$ autoreconf -i # 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 <libunwind-devel@nongnu.org>.
You can do this by sending an email to <libunwind-request@nongnu.org> 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>.
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