The compression ratio benefits are small but consistent, i.e. always positive.
On `silesia.tar` corpus, this modification saves ~75 KB at level 3.
The measured speed cost is negligible, i.e. below noise level, between 0 and -1%.
Sanity checks on a few of the context parameters (i.e. workers and block size)
may prompt an early return on ZSTD_generateSequences.
Allocating the destination buffer past those return points avoids a potential
memory leak.
This patch should fix issue #4112.
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.
Commit f4dbfce79cb2b82fb496fcd2518ecd3315051b7d ("define LIB_SRCDIR
and LIB_BINDIR") significantly reworked the build logic, but in its
introduction of LIB_BINDIR a typo was made.
It was introduced as such:
+LIB_SRCDIR ?= $(dir $(realpath $(lastword $(MAKEFILE_LIST))))
+LIB_BINDIR ?= $(LIBSRC_DIR)
But the definition of LIB_BINDIR has a typo: it should use
$(LIB_SRCDIR) not $(LIBSRC_DIR).
Due to this, $(LIB_BINDIR) is empty, therefore in programs/Makefile,
-L$(LIB_BINDIR) is expanded to just -L, and consequently when trying
to link the "zstd" binary with the libzstd library, it cannot find it:
host/lib/gcc/powerpc64-buildroot-linux-gnu/13.3.0/../../../../powerpc64-buildroot-linux-gnu/bin/ld: cannot find -lzstd: No such file or directory
This commit fixes the build by fixing this typo.
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
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
- switched the patter and input of $filter into the right places
- added pattern wildcard to MSYS_NT & CYGWIN_NT as they change with windows versions
- correctly identify MSYS2, even in an env like MINGW64
As reported by Ben Hawkes in #4026, a failure to allocate a zstd context
would lead to a dereference of a NULL pointer due to a missing check
on the returned result of ZSTDv06_createDCtx().
This patch fix the issue by adding a check for valid returned pointer.
Multi-threaded static library require -pthread to correctly link and works.
The pkg-config we provide tho only works with dynamic multi-threaded library
and won't provide the correct libs and cflags values if lib-mt is used.
To handle this, introduce an env variable MT to permit advanced user to
install and generate a correct pkg-config file for lib-mt or detect if
lib-mt target is called.
With MT env set on calling make install-pc, libzstd.pc.in is a
pkg-config file for a multi-threaded static library.
On calling make lib-mt, a libzstd.pc is generated for a multi-threaded
static library as it's what asked by the user by forcing it.
libzstd.pc is changed to PHONY to force regeneration of it on calling
lib targets or install-pc to handle case where the same directory is
used for mixed compilation.
This was notice while migrating from meson to make build system where
meson generates a correct .pc file while make doesn't.
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
This function was seriously flawed:
* It didn't do output bounds checks
* It produced invalid sequences when an uncompressed or RLE block was emitted
* It produced invalid sequences when the block splitter was enabled
* It produced invalid sequences when ZSTD_c_targetCBlockSize was enabled
I've attempted to fix these issues, but this function is just a bad idea,
so I've marked it as deprecated and unsafe. We should replace it with
`ZSTD_extractSequences()` which operates on a compressed frame.
