This type is useful for two things:
* Doing non-local control flow with ucontext.h functions.
* Inspecting machine state in a signal handler.
The first use case is not one we support; we no longer expose bindings to those
functions in the standard library. They're also deprecated in POSIX and, as a
result, not available in musl.
The second use case is valid, but is very poorly served by the standard library.
As evidenced by my changes to std.debug.cpu_context.signal_context_t, users will
be better served rolling their own ucontext_t and especially mcontext_t types
which fit their specific situation. Further, these types tend to evolve
frequently as architectures evolve, and the standard library has not done a good
job keeping up, or even providing them for all supported targets.
I made a couple of decisions for this based on the fact that we don't expose the
signal_ucontext_t type outside of the file:
* Adding all the floating point and vector state to every ucontext_t and
mcontext_t variant was way, way too much work, especially when we don't even
use the stuff. So I deleted all that and kept only the bare minimum needed to
reach into general-purpose registers.
* There is no particularly compelling reason to stick to the naming and struct
nesting used in the system headers. So we can actually unify the access
patterns for almost all of these variants by taking some liberties here; as a
result, fromPosixSignalContext() is now much nicer to read and extend.
I broke this when porting this logic for the `std.debug` rework in
https://github.com/ziglang/zig/pull/25227. The offset that I copied was
actually being treated as relative to the address of the *saved* base
pointer. I think it makes more sense to do what I did and just treat all
offsets as relative to this frame's base.
Now it's based on calling fillMore rather than an illegal aliased stream
into the Reader buffer.
This commit also includes a disambiguation block inspired by #25162. If
`StreamTooLong` was added to `RebaseError` then this logic could be
replaced by removing the exit condition from the while loop. That error
code would represent when `buffer` capacity is too small for an
operation, replacing the current use of asserts.
Fix `takeDelimiter` and `takeDelimiterExclusive` tossing too many bytes
(#25132)
Also add/improve test coverage for all delimiter and sentinel methods,
update usages of `takeDelimiterExclusive` to not rely on the fixed bug,
tweak a handful of doc comments, and slightly simplify some logic.
I have not fixed#24950 in this commit because I am a little less
certain about the appropriate solution there.
Resolves: #25132
Co-authored-by: Andrew Kelley <andrew@ziglang.org>
* File.Writer.seekBy passed wrong offset to setPosAdjustingBuffer.
* File.Writer.sendFile incorrectly used non-logical position.
Related to 1d764c1fdf04829cec5974d82cec901825a80e49
Test case provided by:
Co-authored-by: Kendall Condon <goon.pri.low@gmail.com>
Previously, the logic in peekDelimiterInclusive (when the delimiter was not found in the existing buffer) used the `n` returned from `r.vtable.stream` as the length of the slice to check, but it's valid for `vtable.stream` implementations to return 0 if they wrote to the buffer instead of `w`. In that scenario, the `indexOfScalarPos` would be given a 0-length slice so it would never be able to find the delimiter.
This commit changes the logic to assume that `r.vtable.stream` can both:
- return 0, and
- modify seek/end (i.e. it's also valid for a `vtable.stream` implementation to rebase)
Also introduces `std.testing.ReaderIndirect` which helps in being able to test against Reader implementations that return 0 from `stream`/`readVec`
Fixes#25428
This reverts commit 27aba2d776caf59bb6569934626af587fdba9c75.
I'd like to review this contribution more carefully, particularly with
the alternate implementation that is also open as a pull request
(#25109).
Reopens#25093
`findScalarPos` might do repetitive work, even if using simd. For
example, when searching the string `/abcde/fghijk/lm` for the character
`/`, a 16-byte wide search would yield `1000001000000100` but would only
count the first `1` and re-search the remaining of the string.
When testing locally, the difference was quite significative:
```
count scalar
5737 iterations 522.83us per iterations
0 bytes per iteration
worst: 2370us median: 512us stddev: 107.64us
count v2
38333 iterations 78.03us per iterations
0 bytes per iteration
worst: 713us median: 76us stddev: 10.62us
count scalar v2
99565 iterations 29.80us per iterations
0 bytes per iteration
worst: 41us median: 29us stddev: 1.04us
```
Note that `count v2` is a simpler string search, similar to the
remaining version of the simd approach:
```
pub fn countV2(comptime T: type, haystack: []const T, needle: T) usize {
const n = haystack.len;
if (n < 1) return 0;
var count: usize = 0;
for (haystack[0..n]) |item| {
count += @intFromBool(item == needle);
}
return count;
}
```
Which implies the compiler yields some optimized code for a simpler loop
that is more performant than the `findScalarPos`-based approach, hence
the usage of iterative approach for the remaining of the haystack.
Co-authored-by: StAlKeR7779 <stalkek7779@yandex.ru>
For unwinding purposes, we don't care about unsupported registers. Yet because
we added these rules to the cache entry, we'd later try to evaluate them and
thus fail the unwind attempt for no good reason. They'd also take up cache rule
slots that would be better spent on actually relevant registers.
Note that any attempt to read unsupported registers during unwinding will still
fail the unwind attempt as expected.
* ELF v1 on powerpc64 is only barely kept on life support in a couple of Linux
distros. I don't anticipate that this will last much longer.
* Most of the Linux world has moved to powerpc64le which requires ELF v2.
* Some Linux distros have even started supporting powerpc64 with ELF v2.
* The BSD world has long since moved to ELF v2.
* We have no actual linking support for ELF v1.
* ELF v1 had confused DWARF register mappings which is becoming a problem in
our DWARF code in std.debug.
It's clear that ELF v1 is on its way out, and we never fully supported it
anyway. So let's not waste any time or energy on it going forward.
closes#5927
