I should have always known this but I didn't. Here is an example
as a reminder to myself:
int mycopy(void *dest, void *src, size_t n)
{
memcpy(dest, src, n);
return dest == NULL;
}
In the example, a compiler may assume that dest != NULL because
passing NULL to memcpy() would be undefined behavior. Testing
with GCC 8.2.1, mycopy(NULL, NULL, 0) returns 1 with -O0 and -O1.
With -O2 the return value is 0 because the compiler infers that
dest cannot be NULL because it was already used with memcpy()
and thus the test for NULL gets optimized out.
In liblzma, if a null-pointer was passed to memcpy(), there were
no checks for NULL *after* the memcpy() call, so I cautiously
suspect that it shouldn't have caused bad behavior in practice,
but it's hard to be sure, and the problematic cases had to be
fixed anyway.
Thanks to Jeffrey Walton.
"xz -dcfv not_an_xz_file" crashed (all four options are
required to trigger it). It caused xz to call
lzma_get_progress(&strm, ...) when no coder was initialized
in strm. In this situation strm.internal is NULL which leads
to a crash in lzma_get_progress().
The bug was introduced when xz started using lzma_get_progress()
to get progress info for multi-threaded compression, so the
bug is present in versions 5.1.3alpha and higher.
Thanks to Filip Palian <Filip.Palian@pjwstk.edu.pl> for
the bug report.
I understood that if a WTPV is specified, it's often wrong
because different VS installations have different SDK version
installed. Omitting the WTPV tag makes VS2017 default to
Windows SDK 8.1 which often is also missing, so in any case
people may need to specify the WTPV before building. But some
day in the future a missing WTPV tag will start to default to
the latest installed SDK which sounds reasonable:
https://developercommunity.visualstudio.com/content/problem/140294/windowstargetplatformversion-makes-it-impossible-t.html
Thanks to "dom".
It ended up printing an uninitialized char-array when trying to
print the check names (column 7) on the "totals" line.
This also changes the column 12 (minimum xz version) to
50000002 (xz 5.0.0) instead of 0 when there are no valid
input files.
Thanks to kidmin for the bug report.
The 0 got treated specially in a buggy way and as a result
the function did nothing. The API doc said that 0 was supposed
to return LZMA_PROG_ERROR but it didn't.
Now 0 is treated as if 1 had been specified. This is done because
0 is already used to indicate an error from lzma_memlimit_get()
and lzma_memusage().
In addition, lzma_memlimit_set() no longer checks that the new
limit is at least LZMA_MEMUSAGE_BASE. It's counter-productive
for the Index decoder and was actually needed only by the
auto decoder. Auto decoder has now been modified to check for
LZMA_MEMUSAGE_BASE.
It returned LZMA_PROG_ERROR, which was done to avoid zero as
the limit (because it's a special value elsewhere), but using
LZMA_PROG_ERROR is simply inconvenient and can cause bugs.
The fix/workaround is to treat 0 as if it were 1 byte. It's
effectively the same thing. The only weird consequence is
that then lzma_memlimit_get() will return 1 even when 0 was
specified as the limit.
This fixes a very rare corner case in xz --list where a specific
memory usage limit and a multi-stream file could print the
error message "Internal error (bug)" instead of saying that
the memory usage limit is too low.
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.
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.
Lasse Collin
Antoine Cœur
Pavel Raiskup
Julien Marrec
Ben Boeckel
Alexey Tourbin