On MicroBlaze, GCC 12 is broken in sense that
__has_attribute(__symver__) returns true but it still doesn't
support the __symver__ attribute even though the platform is ELF
and symbol versioning is supported if using the traditional
__asm__(".symver ...") method. Avoiding the traditional method is
good because it breaks LTO (-flto) builds with GCC.
See also: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101766
For now the only extra symbols in liblzma_linux.map are the
compatibility symbols with the patch that spread from RHEL/CentOS 7.
These require the use of __symver__ attribute or __asm__(".symver ...")
in the C code. Compatibility with the patch from CentOS 7 doesn't
seem valuable on MicroBlaze so use liblzma_generic.map on MicroBlaze
instead. It doesn't require anything special in the C code and thus
no LTO issues either.
An alternative would be to detect support for __symver__
attribute in configure.ac and CMakeLists.txt and fall back
to __asm__(".symver ...") but then LTO would be silently broken
on MicroBlaze. It sounds likely that MicroBlaze is a special
case so let's treat it as a such because that is simpler. If
a similar issue exists on some other platform too then hopefully
someone will report it and this can be reconsidered.
(This doesn't do the same fix in CMakeLists.txt. Perhaps it should
but perhaps CMake build of liblzma doesn't matter much on MicroBlaze.
The problem breaks the build so it's easy to notice and can be fixed
later.)
Thanks to Vincent Fazio for reporting the problem and proposing
a patch (in the end that solution wasn't used):
https://github.com/tukaani-project/xz/pull/32
It not only makes no sense to put symbol versions into a static library
but it can also cause breakage.
By default Libtool #defines PIC if building a shared library and
doesn't define it for static libraries. This is documented in the
Libtool manual. It can be overriden using --with-pic or --without-pic.
configure.ac detects if --with-pic or --without-pic is used and then
gives an error if neither --disable-shared nor --disable-static was
used at the same time. Thus, in normal situations it works to build
both shared and static library at the same time on GNU/Linux,
only --with-pic or --without-pic requires that only one type of
library is built.
Thanks to John Paul Adrian Glaubitz from Debian for reporting
the problem that occurred on ia64:
https://www.mail-archive.com/xz-devel@tukaani.org/msg00610.html
We require Autoconf >= 2.69 and that has AC_CONFIG_HEADERS.
There is a warning about AC_PROG_CC_C99 being obsolete but
it cannot be removed because it is needed with Autoconf 2.69.
RHEL/CentOS 7 shipped with 5.1.2alpha, including the threaded
encoder that is behind #ifdef LZMA_UNSTABLE in the API headers.
In 5.1.2alpha these symbols are under XZ_5.1.2alpha in liblzma.map.
API/ABI compatibility tracking isn't done between development
releases so newer releases didn't have XZ_5.1.2alpha anymore.
Later RHEL/CentOS 7 updated xz to 5.2.2 but they wanted to keep
the exported symbols compatible with 5.1.2alpha. After checking
the ABI changes it turned out that >= 5.2.0 ABI is backward
compatible with the threaded encoder functions from 5.1.2alpha
(but not vice versa as fixes and extensions to these functions
were made between 5.1.2alpha and 5.2.0).
In RHEL/CentOS 7, XZ Utils 5.2.2 was patched with
xz-5.2.2-compat-libs.patch to modify liblzma.map:
- XZ_5.1.2alpha was added with lzma_stream_encoder_mt and
lzma_stream_encoder_mt_memusage. This matched XZ Utils 5.1.2alpha.
- XZ_5.2 was replaced with XZ_5.2.2. It is clear that this was
an error; the intention was to keep using XZ_5.2 (XZ_5.2.2
has never been used in XZ Utils). So XZ_5.2.2 lists all
symbols that were listed under XZ_5.2 before the patch.
lzma_stream_encoder_mt and _mt_memusage are included too so
they are listed both here and under XZ_5.1.2alpha.
The patch didn't add any __asm__(".symver ...") lines to the .c
files. Thus the resulting liblzma.so exports the threaded encoder
functions under XZ_5.1.2alpha only. Listing the two functions
also under XZ_5.2.2 in liblzma.map has no effect without
matching .symver lines.
The lack of XZ_5.2 in RHEL/CentOS 7 means that binaries linked
against unpatched XZ Utils 5.2.x won't run on RHEL/CentOS 7.
This is unfortunate but this alone isn't too bad as the problem
is contained within RHEL/CentOS 7 and doesn't affect users
of other distributions. It could also be fixed internally in
RHEL/CentOS 7.
The second problem is more serious: In XZ Utils 5.2.2 the API
headers don't have #ifdef LZMA_UNSTABLE for obvious reasons.
This is true in RHEL/CentOS 7 version too. Thus now programs
using new APIs can be compiled without an extra #define. However,
the programs end up depending on symbol version XZ_5.1.2alpha
(and possibly also XZ_5.2.2) instead of XZ_5.2 as they would
with an unpatched XZ Utils 5.2.2. This means that such binaries
won't run on other distributions shipping XZ Utils >= 5.2.0 as
they don't provide XZ_5.1.2alpha or XZ_5.2.2; they only provide
XZ_5.2 (and XZ_5.0). (This includes RHEL/CentOS 8 as the patch
luckily isn't included there anymore with XZ Utils 5.2.4.)
Binaries built by RHEL/CentOS 7 users get distributed and then
people wonder why they don't run on some other distribution.
Seems that people have found out about the patch and been copying
it to some build scripts, seemingly curing the symptoms but
actually spreading the illness further and outside RHEL/CentOS 7.
The ill patch seems to be from late 2016 (RHEL 7.3) and in 2017 it
had spread at least to EasyBuild. I heard about the events only
recently. :-(
This commit splits liblzma.map into two versions: one for
GNU/Linux and another for other OSes that can use symbol versioning
(FreeBSD, Solaris, maybe others). The Linux-specific file and the
matching additions to .c files add full compatibility with binaries
that have been built against a RHEL/CentOS-patched liblzma. Builds
for OSes other than GNU/Linux won't get the vaccine as they should
be immune to the problem (I really hope that no build script uses
the RHEL/CentOS 7 patch outside GNU/Linux).
The RHEL/CentOS compatibility symbols XZ_5.1.2alpha and XZ_5.2.2
are intentionally put *after* XZ_5.2 in liblzma_linux.map. This way
if one forgets to #define HAVE_SYMBOL_VERSIONS_LINUX when building,
the resulting liblzma.so.5 will have lzma_stream_encoder_mt@@XZ_5.2
since XZ_5.2 {...} is the first one that lists that function.
Without HAVE_SYMBOL_VERSIONS_LINUX @XZ_5.1.2alpha and @XZ_5.2.2
will be missing but that's still a minor problem compared to
only having lzma_stream_encoder_mt@@XZ_5.1.2alpha!
The "local: *;" line was moved to XZ_5.0 so that it doesn't need
to be moved around. It doesn't matter where it is put.
Having two similar liblzma_*.map files is a bit silly as it is,
at least for now, easily possible to generate the generic one
from the Linux-specific file. But that adds extra steps and
increases the risk of mistakes when supporting more than one
build system. So I rather maintain two files in parallel and let
validate_map.sh check that they are in sync when "make mydist"
is run.
This adds .symver lines for lzma_stream_encoder_mt@XZ_5.2.2 and
lzma_stream_encoder_mt_memusage@XZ_5.2.2 even though these
weren't exported by RHEL/CentOS 7 (only @@XZ_5.1.2alpha was
for these two). I added these anyway because someone might
misunderstand the RHEL/CentOS 7 patch and think that @XZ_5.2.2
(@@XZ_5.2.2) versions were exported too.
At glance one could suggest using __typeof__ to copy the function
prototypes when making aliases. However, this doesn't work trivially
because __typeof__ won't copy attributes (lzma_nothrow, lzma_pure)
and it won't change symbol visibility from hidden to default (done
by LZMA_API()). Attributes could be copied with __copy__ attribute
but that needs GCC 9 and a fallback method would be needed anyway.
This uses __symver__ attribute with GCC >= 10 and
__asm__(".symver ...") with everything else. The attribute method
is required for LTO (-flto) support with GCC. Using -flto with
GCC older than 10 is now broken on GNU/Linux and will not be fixed
(can silently result in a broken liblzma build that has dangerously
incorrect symbol versions). LTO builds with Clang seem to work
with the traditional __asm__(".symver ...") method.
Thanks to Boud Roukema for reporting the problem and discussing
the details and testing the fix.
There is no specific reason for this other than blocking
the most ancient versions. These are still old:
Autoconf 2.69 (2012)
Automake 1.12 (2012)
gettext 0.19.6 (2015)
Libtool 2.4 (2010)
This bumps the version requirement from 0.19 (from 2014) to
0.19.6 (2015).
Using only the old AM_GNU_GETTEXT_VERSION results in old
gettext infrastructure being placed in the package. By using
both macros we get the latest gettext files while the other
programs in the Autotools family can still see the old macro.
I don't know if the problem is in gnulib's gl_POSIX_SHELL macro
or if xzgrep does something that isn't in POSIX. The workaround
adds a special case for Solaris: if /usr/xpg4/bin/sh exists and
gl_cv_posix_shell wasn't overriden on the configure command line,
use that shell for xzgrep and other scripts. That shell is known
to work and exists on most Solaris systems.
This adds a configure option --enable-path-for-scripts=PREFIX
which defaults to empty except on Solaris it is /usr/xpg4/bin
to make POSIX grep and others available. The Solaris case had
been documented in INSTALL with a manual fix but it's better
to do this automatically since it is needed on most Solaris
systems anyway.
Thanks to Daniel Richard G.
In the v5.2 branch this feature is considered experimental
and thus disabled by default.
The sandboxing is used conditionally as described in main.c.
This isn't optimal but it was much easier to implement than
a full sandboxing solution and it still covers the most common
use cases where xz is writing to standard output. This should
have practically no effect on performance even with small files
as fork() isn't needed.
C and locale libraries can open files as needed. This has been
fine in the past, but it's a problem with things like Capsicum.
io_sandbox_enter() tries to ensure that various locale-related
files have been loaded before cap_enter() is called, but it's
possible that there are other similar problems which haven't
been seen yet.
Currently Capsicum is available on FreeBSD 10 and later
and there is a port to Linux too.
Thanks to Loganaden Velvindron for help.
This is the sane thing to do. The conflict with OpenSSL
on some OSes and especially that the OS-provided versions
can be significantly slower makes it clear that it was
a mistake to have the external SHA-256 support enabled by
default.
Those who want it can now pass --enable-external-sha256 to
configure. INSTALL was updated with notes about OSes where
this can be a bad idea.
The SHA-256 detection code in configure.ac had some bugs that
could lead to a build failure in some situations. These were
fixed, although it doesn't matter that much now that the
external SHA-256 is disabled by default.
MINIX >= 3.2.0 uses NetBSD's libc and thus has SHA256_Init
in libc instead of libutil. Support for the libutil version
was removed.
On FreeBSD 10 and older, SHA256_Init from libmd conflicts
with libcrypto from OpenSSL. The OpenSSL version has
different sizeof(SHA256_CTX) and it can cause weird
problems if wrong SHA256_Init gets used.
Looking at the source, MINIX 3 seems to have a similar issue but
I'm not sure. To be safe, I disabled SHA256_Init on MINIX 3 too.
NetBSD has SHA256_Init in libc and they had a similar problem,
but they already fixed it in 2009.
Thanks to Jim Wilcoxson for the bug report that helped
in finding the problem.
The patch is quite long but it's mostly about adding new #ifdefs
to omit code when encoders or decoders have been disabled.
This adds two new #defines to config.h: HAVE_ENCODERS and
HAVE_DECODERS.
Now it gives an error if LZMA1 encoder/decoder is missing
when LZMA2 encoder/decoder was requested. Even better would
be LZMA2 implicitly enabling LZMA1 but it would need more code.
This reverts commit 7a11c4a8e5.
It is a problem when libc has pipe2() but the kernel is too
old to have pipe2() and thus pipe2() fails. In xz it's pointless
to have a fallback for non-functioning pipe2(); it's better to
avoid pipe2() completely.
Thanks to Michael Fox for the bug report.
Clang and nowadays also GCC accept any -Wfoobar option
but then may give a warning that an unknown warning option
was specified. To avoid adding unsupported warning options,
the options are now tested with -Werror.
Thanks to Charles Diza.
This commit just adds the function. Its uses will be in
separate commits.
This hasn't been tested much yet and it's perhaps a bit early
to commit it but if there are bugs they should get found quite
quickly.
Thanks to Jun I Jin from Intel for help and for pointing out
that string comparison needs to be optimized in liblzma.
Now liblzma only uses "mythread" functions and types
which are defined in mythread.h matching the desired
threading method.
Before Windows Vista, there is no direct equivalent to
pthread condition variables. Since this package doesn't
use pthread_cond_broadcast(), pre-Vista threading can
still be kept quite simple. The pre-Vista code doesn't
use anything that wasn't already available in Windows 95,
so the binaries should run even on Windows 95 if someone
happens to care.
Previously it was done in configure, but doing that goes
against the Autoconf manual. Autoconf requires that it is
possible to override e.g. prefix after running configure
and that doesn't work correctly if liblzma.pc is created
by configure.
A potential downside of this change is that now e.g.
libdir in liblzma.pc is a standalone string instead of
being defined via ${prefix}, so if one overrides prefix
when running pkg-config the libdir won't get the new value.
I don't know if this matters in practice.
Thanks to Vincent Torri.
It should actually still work with Automake 1.10 if
the serial-tests option is removed. Automake 1.13 started
using parallel tests by default and the option to get
the old behavior isn't supported before 1.12.
At least for now, parallel tests don't improve anything
in XZ Utils but they hide the progress output from
test_compress.sh.
Variable-length arrays are mandatory in C99 but optional in C11.
The code doesn't currently use any VLAs and it shouldn't in the
future either to stay compatible with C11 without requiring any
optional C11 features.
The scripts are now made executable in the build tree.
This way the scripts can be run like programs in
test_scripts.sh. Previously test_scripts.sh always
used sh but it's not correct if @POSIX_SHELL@ is set
to something else by configure.
Thanks to Jonathan Nieder for the patch.
Symbol versioning is enabled by default on GNU/Linux,
other GNU-based systems, and FreeBSD.
I'm not sure how stable this is, so it may need
backward-incompatible changes before the next release.
The idea is that alpha and beta symbols are considered
unstable and require recompiling the applications that
use those symbols. Once a symbol is stable, it may get
extended with new features in ways that don't break
compatibility with older ABI & API.
The mydist target runs validate_map.sh which should
catch some probable problems in liblzma.map. Otherwise
I would forget to update the map file for new releases.
If the operating system libc or other base libraries
provide SHA-256, use that instead of our own copy.
Note that this doesn't use OpenSSL or libgcrypt or
such libraries to avoid creating dependencies to
other packages.
This supports at least FreeBSD, NetBSD, OpenBSD, Solaris,
MINIX, and Darwin. They all provide similar but not
identical SHA-256 APIs; everyone is a little different.
Thanks to Wim Lewis for the original patch, improvements,
and testing.
Lasse Collin
Jia Tan