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.
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.
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.
It's a problem at least on OpenBSD which doesn't support
O_NONBLOCK on e.g. /dev/null. I'm not surprised if it's
a problem on other OSes too since this behavior is allowed
in POSIX-1.2008.
The code relying on this behavior was committed in June 2013
and included in 5.1.3alpha released on 2013-10-26. Clearly
the development releases only get limited testing.
I don't know the details but I have an impression that there's
no problem in practice if using GCC since people have built xz
with GCC (without patching xz), but renaming the variable cannot
hurt either.
Thanks to Mark Ashley.
Previously, --block-list and --block-size only worked together
in threaded mode. Boundaries are specified by --block-list, but
--block-size specifies the maximum size for a Block. Now this
works in single-threaded mode too.
Thanks to James M Leddy for the original patch.
Now if --block-list is used in threaded mode, the encoder
won't need to flush at each Block boundary specified via
--block-list. This improves performance a lot, making
threading helpful with --block-list.
The flush timer was reset after LZMA_FULL_FLUSH but since
LZMA_FULL_BARRIER doesn't flush, resetting the timer is
no longer done.
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.
When --flush-timeout=TIMEOUT is used, xz will use
LZMA_SYNC_FLUSH if read() would block and at least
TIMEOUT milliseconds has elapsed since the previous flush.
This can be useful in realtime-like use cases where the
data is simultanously decompressed by another process
(possibly on a different computer). If new uncompressed
input data is produced slowly, without this option xz could
buffer the data for a long time until it would become
decompressible from the output.
If TIMEOUT is 0, the feature is disabled. This is the default.
This commit affects the compression side. Using xz for
the decompression side for the above purpose doesn't work
yet so well because there is quite a bit of input and
output buffering when decompressing.
The --long-help or man page were not updated yet.
The details of this feature may change.
Testing for end of file was no longer correct after full flushing
became possible with --block-size=SIZE and --block-list=SIZES.
There was no bug in practice though because xz just made a few
unneeded zero-byte reads.
This switches units from microseconds to milliseconds.
New clock_gettime(CLOCK_MONOTONIC) will be used if available.
There is still a fallback to gettimeofday().
Now both reading and writing should be without
race conditions with signals.
They might still be signal handling issues left.
Signals are blocked during many operations to avoid
EINTR but it may cause problems e.g. if writing to
stderr blocks when trying to display an error message.
It is possible that a signal to set user_abort arrives right
before a blocking system call is made. In this case the call
may block until another signal arrives, while the wanted
behavior is to make xz clean up and exit as soon as possible.
After this commit, the race condition is avoided with the
input side which already uses non-blocking I/O. The output
side still uses blocking I/O and thus has the race condition.
POSIX says that fcntl(fd, F_SETFL, flags) returns -1 on
error and "other than -1" on success. This is how it is
documented e.g. on OpenBSD too. On Linux, success with
F_SETFL is always 0 (at least accorinding to fcntl(2)
from man-pages 3.51).
Lasse Collin