After fixing some issues with inline assembly in the C backend, the std
cleanups have the side effect of making these functions compatible with
the backend, allowing it to be used on linux without linking libc.
When targeting WebAssembly, we default to building a single-threaded build
as threads are still experimental. The user however can enable a multi-
threaded build by specifying '-fno-single-threaded'. It's a compile-error
to enable this flag, but not also enable shared-memory.
When a thread is detached from the main thread, we automatically
cleanup any allocated memory. For this we first reset the stack-pointer
to the original stack-pointer of the main-thread so we can safely clear
the memory which also contains the thread's stack.
When `join` detects a thread has completed, it will free the allocated
memory of the thread. For this we must first copy the allocator. This is
required as the allocated memory holds a reference to the original
allocator. If we free the memory, we would end up with UB as the
allocator would free itself.
We now reset the Thread ID to 0 and wake up the main thread listening
for the thread to finish. We use inline assembly as we cannot use
the stack to set the thread ID as it could possibly clobber any
of the memory.
Currently, we leak the memory that was allocated for the thread.
We need to implement a way where we can clean up the memory without
using the stack (as the stack is stored inside this same memory).
We now store the original allocator that was used to allocate the
memory required for the thread. This allocator can then be used
in any cleanup functionality to ensure the memory is freed correctly.
Secondly, we now use a function to set the stack pointer instead of
generating a function using global assembly. This is a lot cleaner
and more readable.
This implements a first version to spawn a WASI-thread. For a new thread
to be created, we calculate the size required to store TLS, the new stack,
and metadata. This size is then allocated using a user-provided allocator.
After a new thread is spawn, the HOST will call into our bootstrap procedure.
This bootstrap procedure will then initialize the TLS segment and set the
newly spawned thread's TID. It will also set the stack pointer to the newly
created stack to ensure we do not clobber the main thread's stack.
When bootstrapping the thread is completed, we will call the user's
function on this new thread.
Most of this migration was performed automatically with `zig fmt`. There
were a few exceptions which I had to manually fix:
* `@alignCast` and `@addrSpaceCast` cannot be automatically rewritten
* `@truncate`'s fixup is incorrect for vectors
* Test cases are not formatted, and their error locations change
Anecdote 1: The generic version is way more popular than the non-generic
one in Zig codebase:
git grep -w alignForward | wc -l
56
git grep -w alignForwardGeneric | wc -l
149
git grep -w alignBackward | wc -l
6
git grep -w alignBackwardGeneric | wc -l
15
Anecdote 2: In my project (turbonss) that does much arithmetic and
alignment I exclusively use the Generic functions.
Anecdote 3: we used only the Generic versions in the Macho Man's linker
workshop.
- fix getdents return type usize → c_int
- special-case process.zig to use sysctl instead of sysctlbyname
- use struct/field pattern for sysctl HW_* constants
The majority of these are in comments, some in doc comments which might
affect the generated documentation, and a few in parameter names -
nothing that should be breaking, however.
Tests that only reference decls for the purpose of analyzing more tests
should be unnamed, otherwise trying to filter for just a referenced test
can become impossible depending on the names.
OpenBSD 7.3 changed its implementation of
pthread_get_name_np/pthread_set_name_np to wrap new libc functions
getthrname/setthrname and lowered the max buffer size from 32 to 24.
This is not a backwards-compatible change because if we were to put in
comptime version logic to use size 32 when target < 7.3 the binaries
would be undefined when running on >= 7.3. It also could simply be that
OpenBSD has a policy to not support older binaries running on newer
releases? Regardless, the safest course is to simply use the smallest
known buffer size.
As an aside, this bug manifested as a "hung" std.Thread test because 7.3
pthread API never checks for error result when wrapping getthrname/setthrname.
This is not a problem in std.Thread when we use the correct max buffer
size because ERANGE/EINVAL become unreachable.
Man page for posix lists EMFILE, man page for linux ENFILE.
Also posix says "The mmap() function adds an extra reference to the file
associated with the file descriptor fildes which is not removed by a
subsequent close() on that file descriptor. This reference is removed
when there are no more mappings to the file."
It sounds counter-intuitive, that a process limit but no system limit can
be exceeeded.
As far as I understand, fildes is only used for file descriptor backed mmaps.
I believe the reason we had that check in the first place was because for both `pthread_setname_np` and `pthread_getname_np` man says:
```
CONFORMING TO
These functions are nonstandard GNU extensions; hence the suffix "_np" (nonportable) in the names.
```
However, this `is_gnu` check was never consistently applied; it was
missing in `setName` in the Linux case. It is also missing on all other call sites for other platforms (macOS, iOS, et al.).
Though, that could be because it may only apply to Linux.
I think for a best-effort approach it is okay to drop this. It's probably less non-standard than man makes it out to be.
I noticed a comment saying that the intent of a code's author was unclear.
What happened is that the author forgot to put the check for whether the
thread is the calling thread (`self.getHandle() ==
std.c.pthread_self()`) in the `if (use_pthreads)`.
If the thread is the calling thread, we use `prctl` to set or get the
thread's name and it does not take a thread id because it knows the id
of the thread we're calling `getName` or `setName` from.
I have found a source saying that using `pthread_setname_np` on either the calling thread
or any other thread by thread id would work too (so we don't need to
call `prctl`) but I was not sure if that is the case on all systems
so we keep using `pthread_setname_np` if we have a
specific thread that is not the thread we're calling from, and `prctl`
otherwise.
These functions are currently footgunny when working with pointers to
arrays and slices. They just return the stated length of the array/slice
without iterating and looking for the first sentinel, even if the
array/slice is a sentinel terminated type.
From looking at the quite small list of places in the standard
library/compiler that this change breaks existing code, the new code
looks to be more readable in all cases.
The usage of std.mem.span/len was totally unneeded in most of the cases
affected by this breaking change.
We could remove these functions entirely in favor of other existing
functions in std.mem such as std.mem.sliceTo(), but that would be a
somewhat nasty breaking change as std.mem.span() is very widely used for
converting sentinel terminated pointers to slices. It is however not at
all widely used for anything else.
Therefore I think it is better to break these few non-standard and
potentially incorrect usages of these functions now and at some later
time, if deemed worthwhile, finally remove these functions.
If we wait for at least a full release cycle so that everyone adapts to
this change first, updating for the removal could be a simple find and
replace without needing to worry about the semantics.
Previously, this function used incorrect registers for the munmap syscall, leading to detached threads not cleaning up.
closes#12690
Co-authored-by: bxlr <biexelar@diroot.org>
Rename all references of sparcv9 to sparc64, to make Zig align more with
other projects. Also, added new function to convert glibc arch name to Zig
arch name, since it refers to the architecture as sparcv9.
This is based on the suggestion by @kubkon in PR 11847.
(https://github.com/ziglang/zig/pull/11487#pullrequestreview-963761757)
