Do some include shuffling for `**.h` files within lib, programs, tests, and zlibWrapper.
`lib/legacy` and `lib/deprecated` are untouched.
`#include`s within `extern "C"` blocks in .cpp files are untouched.
todo: shuffling for `xxhash.h`
The NDK cross compiler declares the target as __linux (which is
not technically incorrect), which triggers the enablement of _GNU_SOURCE
in the newly added code that requires the presence of qsort_r() used
in the COVER dictionary code.
Even though the NDK uses llvm/libc, it doesn't declare qsort_r()
in the stdlib.h header.
The build fix is to only activate the _GNU_SOURCE macro if the OS is
*not* Android, as then we will fallback to the C90 compliant code.
This patch should solve the reported issue number #4103.
The two main functions used for dictionary training using the COVER
algorithm require initialization of a COVER_ctx_t where a call
to qsort() is performed.
The issue is that the standard C99 qsort() function doesn't offer
a way to pass an extra parameter for the comparison function callback
(e.g. a pointer to a context) and currently zstd relies on a *global*
static variable to hold a pointer to a context needed to perform
the sort operation.
If a zstd library user invokes either ZDICT_trainFromBuffer_cover or
ZDICT_optimizeTrainFromBuffer_cover from multiple threads, the
global context may be overwritten before/during the call/execution to qsort()
in the initialization of the COVER_ctx_t, thus yielding to crashes
and other bad things (Tm) as reported on issue #4045.
Enters qsort_r(): it was designed to address precisely this situation,
to quote from the documention [1]: "the comparison function does not need to
use global variables to pass through arbitrary arguments, and is therefore
reentrant and safe to use in threads."
It is available with small variations for multiple OSes (GNU, BSD[2],
Windows[3]), and the ISO C11 [4] standard features on annex B-21 qsort_s() as
part of the <stdlib.h>. Let's hope that compilers eventually catch up
with it.
For now, we have to handle the small variations in function parameters
for each platform.
The current fix solves the problem by allowing each executing thread
pass its own COVER_ctx_t instance to qsort_r(), removing the use of
a global pointer and allowing the code to be reentrant.
Unfortunately for *BSD, we cannot leverage qsort_r() given that its API
has changed on newer versions of FreeBSD (14.0) and the other BSD variants
(e.g. NetBSD, OpenBSD) don't implement it.
For such cases we provide a fallback that will work only requiring support
for compilers implementing support for C90.
[1] https://man7.org/linux/man-pages/man3/qsort_r.3.html
[2] https://man.freebsd.org/cgi/man.cgi?query=qsort_r
[3] https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/qsort-s?view=msvc-170
[4] https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1548.pdf
This PR introduces no functional changes. It attempts to change all
macros currently using `{ }` or some variant of that to to
`do { } while (0)`, and introduces trailing `;` where necessary.
There were no bugs found during this migration.
The bug in Visual Studios warning on this has been fixed since VS2015.
Additionally, we have several instances of `do { } while (0)` which have
been present for several releases, so we don't have to worry about
breaking peoples builds.
Fixes Issue #3830.
the flexArray in structure FSE_DecompressWksp
is just a way to derive a pointer easily,
without risk/complexity of calculating it manually.
Not sure if this change is good enough to avoid ubsan warnings though.
* Remove all pointer-overflow suppressions from our UBSAN builds/tests.
* Add `ZSTD_ALLOW_POINTER_OVERFLOW_ATTR` macro to suppress
pointer-overflow at a per-function level. This is a superior approach
because it also applies to users who build zstd with UBSAN.
* Add `ZSTD_wrappedPtr{Diff,Add,Sub}()` that use these suppressions.
The end goal is to only tag these functions with
`ZSTD_ALLOW_POINTER_OVERFLOW`. But we can start by annoting functions
that rely on pointer overflow, and gradually transition to using
these.
* Add `ZSTD_maybeNullPtrAdd()` to simplify pointer addition when the
pointer may be `NULL`.
* Fix all the fuzzer issues that came up. I'm sure there will be a lot
more, but these are the ones that came up within a few minutes of
running the fuzzers, and while running GitHub CI.
The Huffman repeat mode checker assumed that the CTable was zeroed in the region `[maxSymbolValue + 1, 256)`.
This assumption didn't hold for tables built in the dictionaries, because it didn't go through the same codepath.
Since this code was originally written, we added a header to the CTable that specifies the `tableLog`.
Add `maxSymbolValue` to that header, and check that the table's `maxSymbolValue` is at least the block's `maxSymbolValue`.
This solution is cleaner because we write this header for every CTable we build, so it can't be missed in any code path.
Credit to OSS-Fuzz
The sequence section starts with a number, which tells how sequences are present in the section.
If this number if 0, the section automatically ends.
The number 0 can be represented using the 1 byte or the 2 bytes formats.
That's because the 2-bytes formats fully overlaps the 1 byte format.
However, when 0 is represented using the 2-bytes format,
the decoder was expecting the sequence section to continue,
and was looking for FSE tables, which is incorrect.
Fixed this behavior, in both the reference decoder and the educational behavior.
In practice, this behavior never happens,
because the encoder will always select the 1-byte format to represent 0,
since this is more efficient.
Completed the fix with a new golden sample for tests,
a clarification of the specification,
and a decoder errata paragraph.
Inlining `BIT_reloadDStream` provided >3% decompression speed improvement for
clang PGO-optimized zstd binary, measured using the Silesia corpus with
compression level 1. The win comes from improved register allocation which leads
to fewer spills and reloads. Take a look at this comparison of
profile-annotated hot assembly before and after this change:
https://www.diffchecker.com/UjDGIyLz/. The diff is a bit messy, but notice three
fewer moves after inlining.
In general LLVM's register allocator works better when it can see more code. For
example, when the register allocator sees a call instruction, it partitions the
registers into caller registers and callee registers, and it is not free to do
whatever it wants with all the registers for the current function. Inlining the
callee lets the register allocation access all registers and use them more
flexsibly.
Part 2 of #3528
Adds hash salt that helps to avoid regressions where consecutive compressions use the same tag space with similar data (running zstd -b5e7 enwik8 -B128K reproduces this regression).
- Adds memory type that is guaranteed to have been initialized at least once in the workspace's lifetime.
- Changes tag space in row hash to be based on init once memory.
* 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
