In general, I don't like the idea of std.meta.trait, and so I am
providing some guidance by deleting the entire namespace from the
standard library and compiler codebase.
My main criticism is that it's overcomplicated machinery that bloats
compile times and is ultimately unnecessary given the existence of Zig's
strong type system and reference traces.
Users who want this can create a third party package that provides this
functionality.
closes#18051
Justification: It is common for non-CPU bound short routines to do
non-blocking accept to eliminate unnecessary delays before subscribing
to data, for example in hardware integration tests.
```zig
const std = @import("std");
pub fn main() !void {
var addr: *u8 = @ptrFromInt(0xaaaaaaaaaaaaaaaa);
addr.* = 1;
}
```
On x86_64-linux:
Before:
```
$ zig run x.zig
Segmentation fault at address 0x0
/home/wooster/Desktop/zig/x.zig:5:5: 0x21d887 in main (x)
addr.* = 1;
^
/home/wooster/Desktop/zig-linux-x86_64/lib/std/start.zig:583:37: 0x21d847 in posixCallMainAndExit (x)
const result = root.main() catch |err| {
^
/home/wooster/Desktop/zig-linux-x86_64/lib/std/start.zig:251:5: 0x21d371 in _start (x)
asm volatile (switch (native_arch) {
^
???:?:?: 0x0 in ??? (???)
Aborted (core dumped)
```
After:
```
$ zig run x.zig --zig-lib-dir lib
General protection exception
/home/wooster/Desktop/zig/x.zig:5:5: 0x21d907 in main (x)
addr.* = 1;
^
/home/wooster/Desktop/zig/lib/std/start.zig:583:37: 0x21d8c7 in posixCallMainAndExit (x)
const result = root.main() catch |err| {
^
/home/wooster/Desktop/zig/lib/std/start.zig:251:5: 0x21d3f1 in _start (x)
asm volatile (switch (native_arch) {
^
???:?:?: 0x0 in ??? (???)
Aborted (core dumped)
```
As @IntegratedQuantum pointed out in <https://github.com/ziglang/zig/issues/17745#issuecomment-1783815386>,
it seems that if `code` of the `siginfo_t` instance is a certain value (128), you are able to distinguish between
a general protection exception and a segmentation fault.
This does not seem to be documented on `man sigaction`:
```
The following values can be placed in si_code for a SIGSEGV signal:
SEGV_MAPERR
Address not mapped to object.
SEGV_ACCERR
Invalid permissions for mapped object.
SEGV_BNDERR (since Linux 3.19)
Failed address bound checks.
SEGV_PKUERR (since Linux 4.6)
Access was denied by memory protection keys. See pkeys(7). The protection key which applied to this access is available via si_pkey.
```
(those constants are 1, 2, 3, and 4; none of them are the 128)
I can't find a lot of documentation about this but it seems to work consistently for me on x86_64-linux.
Here is a gist which provides additional evidence that this is a reliable way of checking for a general protection fault:
https://gist.github.com/ytoshima/5682393 (read comment in first line)
See also: https://stackoverflow.com/questions/64309366/why-is-the-segfault-address-null-when-accessing-memory-that-has-any-of-the-16-mo
This only seems to affect x86_64 and on 32-bit x86 this does not seem to be a problem.
Helps with #17745 but doesn't close it because the issue still exists on Windows and other POSIX OSs.
I also limited this to x86_64-linux for now because that's the only platform where I tested it. Might work on more POSIX OSs.
Instead of `zig init-lib` and `zig init-exe`, now there is only
`zig init`, which initializes any of the template files that do not
already exist, and makes a package that contains both an executable and
a static library. The idea is that the user can delete whatever they
don't want. In fact, I think even more things should be added to the
build.zig template.
Seems like this restriction was actual when Ziglang had extern enums,
but now it's not neccessary and can be lifted. It was present since
original PR which introduced std.enums, https://www.github.com/ziglang/zig/pull/8171.
See also: https://ziggit.dev/t/catching-invalid-enum-value-errors/2206/11
* Make `count` comptime_int instead of usize
With previous type, creating EnumIndexer for enum(usize) and enum(isize)
would cause compile error since `count` could not store maxInt(usize) + 1.
Now it can store it and reflects len field from std.builtin.Type.Array
(most common use case of count field inside std.enums functions is creating arrays).
Signed-off-by: Eric Joldasov <bratishkaerik@getgoogleoff.me>
This change fixes some division-by-zero bugs introduced by the optimized
ring buffer read/write functions in d8c067966.
There are edge cases where decompression can use a length zero ring
buffer as the size of the ring buffer used is exactly the the window
size specified by a Zstandard frame, and this can be zero. Switching
away from loops to mem copies means that we need to ensure ring buffers
do not have length zero ring when attempting to read/write from them.
There is no grantee that `copy_cqes` will return exactly wait_nr number of cqes.
If there are ready cqes it can return > 0 but < wait_nr number of cqes.
The low-level `Curve25519.fromEdwards25519()` function assumed
that the X/Y coordinates were not scaled (Z=1).
But this is not guaranteed to be the case.
In most real-world applications, the coordinates are freshly decoded,
either directly or via the `X25519.fromEd25519()` function, so this
is not an issue.
However, since we offer the ability to do that conversion after
arbitrary computations, the assertion was not correct.
Perform these transformations in this priority order:
1. If the `else` expression is missing or an empty block, replace the condition with `if (true)` if it is not already.
2. If the `then` block is empty, replace the condition with `if (false)` if it is not already.
3. If the condition is `if (true)`, replace the `if` expression with the contents of the `then` expression.
4. If the condition is `if (false)`, replace the `if` expression with the contents of the `else` expression.
Server networking application typically accept multiple connections. Multishot
accept simplifies handling these situations. Applications submits once and
receives CQE whenever a new connection request comes in.
Multishot is active until it is canceled or experience error. While active, and
further notification are expected CQE completion will have IORING_CQE_F_MORE set
in the flags. If this flag isn't set, the application must re-arm this request
by submitting a new one.
Reference: [io_uring and networking in 2023](https://github.com/axboe/liburing/wiki/io_uring-and-networking-in-2023#multi-shot)
