The block splitter confuses sequences with literal length == 65536 that use a
repeat offset code. It interprets this as literal length == 0 when deciding the
meaning of the repeat offset, and corrupts the repeat offset history. This is
benign, merely causing suboptimal compression performance, if the confused
history is flushed before the end of the block, e.g. if there are 3 consecutive
non-repeat code sequences after the mistake. It also is only triggered if the
block splitter decided to split the block.
All that to say: This is a rare bug, and requires quite a few conditions to
trigger. However, the good news is that if you have a way to validate that the
decompressed data is correct, e.g. you've enabled zstd's checksum or have a
checksum elsewhere, the original data is very likely recoverable. So if you were
affected by this bug please reach out.
The fix is to remind the block splitter that the literal length is actually 64K.
The test case is a bit tricky to set up, but I've managed to reproduce the issue.
Thanks to @danlark1 for alerting us to the issue and providing us a reproducer!
fix#3500
CMake 3.18 or later was required by #3392. Because it uses
`CheckLinkerFlag`. But requiring CMake 3.18 or later is a bit
aggressive. Because Ubuntu 20.04 LTS still uses CMake 3.16.3:
https://packages.ubuntu.com/search?keywords=cmake
This change disables `-z noexecstack` check with old CMake. This will
not break any existing users. Because users who need `-z noexecstack`
must already use CMake 3.18 or later.
Implemented CI workflow for testing compilation with external compressors and without them. This serves as a sanity check to avoid any code dependencies on libraries that may not always be present. (Reference: #3497 for a bug fix related to this issue.)
Bytef and uInt are zlib types, not available when zlib is disabled
Fixes: 1598e6c634 ("Async write for decompression")
Fixes: cc0657f27d ("AsyncIO compression part 2 - added async read and asyncio to compression code (#3022)")
* Fixes zstd-dll build (https://github.com/facebook/zstd/issues/3492):
- Adds pool.o and threading.o dependency to the zstd-dll target
- Moves custom allocation functions into header to avoid needing to add dependency on common.o
- Adds test target for zstd-dll
- Adds github workflow that buildis zstd-dll
* fix and test MSVC AVX2 build
* treat msbuild warnings as errors
* fix incorrect MSVC 2019 compiler warning
* fix MSVC error D9035: option 'Gm' has been deprecated and will be removed in a future release
We need to run it for the tests, even if programs are disabled. So if
they are disabled, create a build rule for the program, but don't
install it. Just make it available for the test itself.
It depends on the zstd program being built, and passes it as an env
variable. Just like datagen. But for datagen, we explicitly depend on
it, while for zstd, we assume it's built as part of "all".
This can be wrong in two cases:
- when running individual tests, meson can (re)build just what is needed
for that one test
- a later patch will handle building zstd but not by default
This frame is invalid because the `Window_Size = 0`, and the
`Block_Maximum_Size = min(128 KB, Window_Size) = 0`. But the empty
compressed block has a `Block_Content` size of 2, which is invalid.
The fix is to switch to using a `Window_Descriptor` instead of the
`Single_Segment_Flag`. This sets the `Window_Size = 1024`.
Hexdump before this PR: `28b5 2ffd 2000 1500 0000 00`
Hexdump after this PR: `28b5 2ffd 0000 1500 0000 00`
For issue #3482.
