Rather than remove the flag entirely, as proposed in #3499, this commit uses
the newest C++ standard the compiler supports. This retains the selection of
using only standardized features (excluding GNU extensions) and keeps the
recency requirements of the codebase explicit.
Tested with various versions of `g++` and `clang++`.
Note that the `fd` is only valid while the file is still open. So we need to
move the setting calls to before we close the file. However! We cannot do so
with the `utime()` call (even though `futimens()` exists) because the follow-
ing `close()` call to the `fd` will reset the atime of the file. So it seems
the `utime()` call has to happen after the file is closed.
Somewhat surprisingly, calling `fchmod()` is non-trivially faster than calling
`chmod()`, and so on.
This commit introduces alternate variants to some common file util functions
that take an optional fd. If present, they call the `f`-variant of the
underlying function. Otherwise, they fall back to the regular filename-taking
version of the function.
In GCC, we can add a couple more flags to give us confidence that the profile
data is actually being found and used.
Also, my system for example doesn't have a binary installed under the name
`llvm-profdata`, but it does have, e.g., `llvm-profdata-13`, etc. So this
commit adds a variable that can be overridden.
The one that isn't pinned is the OSS-Fuzz builder and runner. They don't
offer tagged releases. I could pin to the current master commit, but I'm not
sure how desirable that is.
```
for f in $(find . \( -path ./.git -o -path ./tests/fuzz/corpora -o -path ./tests/regression/data-cache -o -path ./tests/regression/cache \) -prune -o -type f);
do
sed -i 's/\-2021/-present/' $f;
done
g co HEAD -- .github/workflows/dev-short-tests.yml # fix bad match
```
```
for f in $(find . \( -path ./.git -o -path ./tests/fuzz/corpora \) -prune -o -type f);
do
sed -i 's/Facebook, Inc\./Meta Platforms, Inc. and affiliates./' $f;
done
```
Currently this function actually reads the dict ID from the dictionary's
header, via `ZSTD_getDictID_fromDict()`. But during decompression the decomp-
ressor actually compares the dict ID in the frame header with the dict ID in
the DDict. Now of course the dict ID in the dictionary contents and the dict
ID in the DDict struct *should* be the same. But in cases of memory corrupt-
ion, where they can drift out of sync, it's misleading for this function to
read it again from the dict buffer rather then return the dict ID that will
actually be used.
Also doing it this way avoids rechecking the magic and so on and so it is a
tiny bit more efficient.
This commit avoids checking whether a hashtable write is safe in two of the
three match-found paths in `ZSTD_compressBlock_fast_noDict_generic`. This pro-
duces a ~0.5% speed-up in compression.
A comment in the code describes why we can skip this check in the other two
paths (the repcode check and the first match check in the unrolled loop).
A downside is that in the new position where we make this check, we have not
yet computed `mLength`. We therefore have to avoid writing *possibly* dangerous
positions, rather than the old check which only avoids writing *actually*
dangerous positions. This leads to a miniscule loss in ratio (remember that
this scenario can only been triggered in very negative levels or under incomp-
ressibility acceleration).
We previously triggered release artifact generation on release creation. We
sometimes observed that the action failed to run. I hypothesized that we were
hitting rate limiting or something. I just stumbled across [this documentat-
ion](https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#release), which says:
> Note: Workflows are not triggered for the `created`, `edited`, or `deleted`
> activity types for draft releases. When you create your release through the
> GitHub browser UI, your release may automatically be saved as a draft.
This must have been what was happening. This commit therefore changes the
trigger to the `published` activity. This should be more reliable.
This does have the unfortunate side effect that artifacts won't be generated
or attached until *after* the release has been published, which is what I was
trying to avoid by using the `created` activity. Oh well.
xxHash symbols are present in `libzstd.so`, but they are local and therefore
unavailable outside the lib. There are two possible solutions to the problem.
We could make those symbols global, or we could remove the dependency.
This commit chooses the latter approach. I suppose this comes at the cost of
code size / build time. I'm open to comments on whether this is a good thing
to do, especially since this will apply even when we are statically linking
everything.
This commit makes several changes:
1. It adds modules for the dictionary builder and errors headers.
2. It captures all of the macros that are used to configure these headers.
When the headers are imported as modules and one of these macros is defined
the compiler issues a warning that it needs to be defined on the CLI.
3. It promotes the modulemap file into the root of the lib directory.
Experimentation shows that clang's `-fimplicit-module-maps` will find the
modulemap when placed here, but not when it's put in a subdirectory.
Apparently, even when the assembly file is empty (because
`ZSTD_ENABLE_ASM_X86_64_BMI2` is false), it still is marked as possibly
needing an executable stack and so the whole library is marked as such. This
commit applies a simple patch for this problem by moving the noexecstack
indication outside the macro guard.
This commit builds on #2857.
This commit addresses #2963.
I couldn't find a good way to spread `ip0` and `ip1` apart when we accelerate
due to incompressible inputs. (The methods I tried slowed things down quite a
bit.)
Since we aren't splaying ip0 and ip1 apart (which would be like `0_1_2_3_`, as
opposed to the `01__23__` we were actually doing), it's a big ambitious to
increment `step` by 2. Instead, let's increment it by 1, which has the benefit
sliiightly improving compression. Speed remains pretty much unchanged.
The position updates are rewritten from `ip[N] = ip[N-1] + step` to be
`ip[N] = ip[N-2] + step`. This lets us only deal with the asymmetric spacing
of gaps at setup and then we only have to keep a single `step` variable.
This seems to work quite well on GCC and Clang!
This replicates the behavior of @terrelln's `ZSTD_fast` implementation. That
is, it always looks at adjacent pairs of positions, and only applies the
acceleration every other position. This produces a more fine-grained
acceleration.
