The main goal here was to avoid allocating padding and header space if
`malloc` already guarantees the alignment we need via `max_align_t`.
Previously, the compiler was using `std.heap.raw_c_allocator` as its GPA
in some cases depending on `std.c.max_align_t`, but that's pretty
fragile (it meant we had to encode our alignment requirements into
`src/main.zig`!). Perhaps more importantly, that solution is
unnecessarily restrictive: since Zig's `Allocator` API passes the
`Alignment` not only to `alloc`, but also to `free` etc, we are able to
use a different strategy depending on its value. So `c_allocator` can
simply compare the requested align to `Alignment.of(std.c.max_align_t)`,
and use a raw `malloc` call (no header needed!) if it will guarantee a
suitable alignment (which, in practice, will be true the vast majority
of the time).
So in short, this makes `std.heap.c_allocator` more memory efficient,
and probably removes any incentive to use `std.heap.raw_c_allocator`.
I also refactored the `c_allocator` implementation while doing this,
just to neaten things up a little.
This avoids pessimizing concurrency on all machines due to e.g. the macOS
machine having high memory usage across the board due to 16K page size.
This also adds max_rss to test-unit and test-c-abi since those tend to eat a
decent chunk of memory too.
If ECANCELED occurs, it's from pthread_cancel which will *permanently*
set that thread to be in a "canceling" state, which means the cancel
cannot be ignored. That means it cannot be retried, like EINTR. It must
be acknowledged.
Unfortunately, trying again until the cancellation request is
acknowledged has been observed to incur a large amount of overhead,
and usually strong cancellation guarantees are not needed, so the
race condition is not handled here. Users who want to avoid this
have this menu of options instead:
* Use no libc, in which case Zig std lib can avoid the race (tracking
issue: https://codeberg.org/ziglang/zig/issues/30049)
* Use musl libc
* Use `std.Io.Evented`. But this is not implemented yet. Tracked by
- https://codeberg.org/ziglang/zig/issues/30050
- https://codeberg.org/ziglang/zig/issues/30051
glibc + threaded is the only problematic combination.
On a heavily loaded Linux 6.17.5, I observed a maximum of 20 attempts
not acknowledged before the timeout (including exponential backoff) was
sufficient, despite the heavy load.
The time wasted here sleeping is mitigated by the fact that, later on,
the system will likely wait for the canceled task, causing it to
indefinitely yield until the canceled task finishes, and the task must
acknowledge the cancel before it proceeds to that point.
Now, before a syscall is entered, beginSyscall is called, which may
return error.Canceled. After syscall returns, whether error or success,
endSyscall is called. If the syscall returns EINTR then checkCancel is
called.
`cancelRequested` is removed from the std.Io VTable for now, with plans
to replace it with a more powerful API that allows protection against
cancellation requests.
closes#25751
The inverse MixColumns operation is already used internally for
AES decryption, but it wasn’t exposed in the public API because
it didn’t seem necessary at the time.
Since then, several new AES-based block ciphers and permutations
(such as Vistrutah and Areion) have been developed, and they require
this operation to be implementable in Zig.
Since then, new interesting AES-based block ciphers and permutations
(Vistrutah, Areion, etc). have been invented, and require that
operation to be implementable in Zig.
This was caused a `[0]std.builtin.Type.StructField.Attributes` to be
considered `undefined`, even though that type is OPV so should prefer
its OPV `.{}` over `undefined`.
Resolves: #30039
Basically detect `-idirafter` flag in `NIX_CFLAGS_COMPILE` and treat it like `-isystem`, also detect `NIX_CFLAGS_LINK` environment variable and treat it like the `NIX_LDFLAGS` .
Reference:
74eefb4210/pkgs/build-support/build-fhsenv-chroot/env.nix (L83)
Hybrid KEMs combine a post-quantum secure KEM with a traditional
elliptic curve Diffie-Hellman key exchange.
The hybrid construction provides security against both classical and quantum
adversaries: even if one component is broken, the combined scheme remains
secure as long as the other component holds.
The implementation follows the IETF CFRG draft specification for concrete
hybrid KEMs:
https://datatracker.ietf.org/doc/draft-irtf-cfrg-concrete-hybrid-kems/
