Only one definition was visible in a translation unit.
It avoided a few casts and temp variables but seems that
this hack doesn't work with link-time optimizations in compilers
as it's not C99/C11 compliant.

Fixes:
http://www.mail-archive.com/xz-devel@tukaani.org/msg00279.html

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.

AU_ALIAS was removed because the new version is incompatible
with the old version.

It no longer checks for <sys/capability.h> separately.
It's enough to test for it as part of AC_CHECK_DECL.
The defines HAVE_CAPSICUM_SYS_CAPSICUM_H and
HAVE_CAPSICUM_SYS_CAPABILITY_H were removed as unneeded.
HAVE_SYS_CAPSICUM_H from AC_CHECK_HEADERS is enough.

It no longer does a useless search for the Capsicum library
if the header wasn't found.

Fixed a bug in ACTION-IF-FOUND (the first argument). Specifying
the argument omitted the default action but the given action
wasn't used instead.

AC_DEFINE([HAVE_CAPSICUM]) is now always called when Capsicum
support is found. Previously it was part of the default
ACTION-IF-FOUND which a custom action would override. Now
the default action only prepends ${CAPSICUM_LIB} to LIBS.

The documentation was updated.

Since there as no serial number, "#serial 2" was added.

The file was loaded from this web page:
https://github.com/google/capsicum-test/blob/dev/autoconf/m4/ax_check_capsicum.m4

Thanks to Loganaden Velvindron for pointing it out for me.

lzma_index_dup() calls index_dup_stream() which, in case of
an error, calls index_stream_end() to free memory allocated
by index_stream_init(). However, it illogically didn't
actually free the memory. To make it logical, the tree
handling code was modified a bit in addition to changing
index_stream_end().

Thanks to Evan Nemerson for the bug report.

It's available in glibc (GNU/Linux, GNU/kFreeBSD). It's better
than sysconf(_SC_NPROCESSORS_ONLN) because sched_getaffinity()
gives the number of cores available to the process instead of
the total number of cores online.

As a side effect, this commit fixes a bug on GNU/kFreeBSD where
configure would detect the FreeBSD-specific cpuset_getaffinity()
but it wouldn't actually work because on GNU/kFreeBSD it requires
using -lfreebsd-glue when linking. Now the glibc-specific function
will be used instead.

Thanks to Sebastian Andrzej Siewior for the original patch
and testing.

xz used to call utime() on Windows, but its result gets lost
on close(). Using _futime() seems to work.

Thanks to Martok for reporting the bug:
http://www.mail-archive.com/xz-devel@tukaani.org/msg00261.html

Thanks to Evan Nemerson.

Thanks to Christian Kujau.

It silences a few warnings and most people probably have
0.19 even on stable distributions.

Thanks to Christian Kujau.

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.

When optimizing, GCC can reorder code so that an uninitialized
value gets used in a comparison, which makes Valgrind unhappy.
It doesn't happen when compiled with -O0, which I tend to use
when running Valgrind.

Thanks to Rich Prohaska. I remember this being mentioned long
ago by someone else but nothing was done back then.

It would be too annoying to update other build systems
just because of this.

They all need decoder support and if that isn't available,
there's no point trying to build them.

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.

People shouldn't rely on the presets when decoding raw streams,
but xz uses the presets as the starting point for raw decoder
options anyway.

lzma_encocder_presets.c was renamed to lzma_presets.c to
make it clear it's not used solely by the encoder code.

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.

Previously it was omitted if encoders were disabled
with --disable-encoders. It didn't make sense and
it also broke the build.

If an appropriate header and structure were found by configure,
but a library with a usable SHA-256 functions wasn't, the build
failed.

unlink() can return EBUSY in errno for open files on some
operating systems and file systems.