Initial std library support for NuttX
This PR add the initial libstd support for NuttX platform (Tier 3), currently it depends on https://github.com/rust-lang/libc/pull/3909 which provide the essential libc definitions.
Fix build failure on vxworks #127084
PR to address issue #127084 .
1. Skip `reset_segpipe` for vxworks
2. Return unimplemented error for vxworks from settimes and lchown
3. Temporarily skip dirfd for vxworks
4. Add allow unused unsafe on read_at and write_at functions in unix/fs.rs
5. Using cfg disable ON_BROKEN_PIPE_FLAG_USED and on_broken_pipe_flag_used() for vxworks
6. Remove old crate::syscommon:🧵:min_stack() reference from process_vxworks.rs and update to set stack size of rtpthread
Thank you.
Use pidfd_spawn for faster process spawning when a PidFd is requested
glibc 2.39 added `pidfd_spawnp` and `pidfd_getpid` which makes it possible to get pidfds while staying on the CLONE_VFORK path.
verified that vfork gets used with strace:
```
$ strace -ff -e pidfd_open,clone3,openat,execve,waitid,close ./x test std --no-doc -- pidfd
[...]
[pid 2820532] clone3({flags=CLONE_VM|CLONE_PIDFD|CLONE_VFORK|CLONE_CLEAR_SIGHAND, pidfd=0x7b7f885fec6c, exit_signal=SIGCHLD, stack=0x7b7f88aff000, stack_size=0x9000}strace: Process 2820533 attached
<unfinished ...>
[pid 2820533] execve("/home/the8472/bin/sleep", ["sleep", "1000"], 0x7ffdd0e268d8 /* 107 vars */) = -1 ENOENT (No such file or directory)
[pid 2820533] execve("/home/the8472/.cargo/bin/sleep", ["sleep", "1000"], 0x7ffdd0e268d8 /* 107 vars */) = -1 ENOENT (No such file or directory)
[pid 2820533] execve("/usr/local/bin/sleep", ["sleep", "1000"], 0x7ffdd0e268d8 /* 107 vars */) = -1 ENOENT (No such file or directory)
[pid 2820533] execve("/usr/bin/sleep", ["sleep", "1000"], 0x7ffdd0e268d8 /* 107 vars */ <unfinished ...>
[pid 2820532] <... clone3 resumed> => {pidfd=[3]}, 88) = 2820533
[pid 2820533] <... execve resumed>) = 0
[pid 2820532] openat(AT_FDCWD, "/proc/self/fdinfo/3", O_RDONLY|O_CLOEXEC) = 4
[pid 2820532] close(4) = 0
```
Tracking issue: #82971
std: refactor the TLS implementation
As discovered by Mara in #110897, our TLS implementation is a total mess. In the past months, I have simplified the actual macros and their expansions, but the majority of the complexity comes from the platform-specific support code needed to create keys and register destructors. In keeping with #117276, I have therefore moved all of the `thread_local_key`/`thread_local_dtor` modules to the `thread_local` module in `sys` and merged them into a new structure, so that future porters of `std` can simply mix-and-match the existing code instead of having to copy the same (bad) implementation everywhere. The new structure should become obvious when looking at `sys/thread_local/mod.rs`.
Unfortunately, the documentation changes associated with the refactoring have made this PR rather large. That said, this contains no functional changes except for two small ones:
* the key-based destructor fallback now, by virtue of sharing the implementation used by macOS and others, stores its list in a `#[thread_local]` static instead of in the key, eliminating one indirection layer and drastically simplifying its code.
* I've switched over ZKVM (tier 3) to use the same implementation as WebAssembly, as the implementation was just a way worse version of that
Please let me know if I can make this easier to review! I know these large PRs aren't optimal, but I couldn't think of any good intermediate steps.
`@rustbot` label +A-thread-locals
As discovered by Mara in #110897, our TLS implementation is a total mess. In the past months, I have simplified the actual macros and their expansions, but the majority of the complexity comes from the platform-specific support code needed to create keys and register destructors. In keeping with #117276, I have therefore moved all of the `thread_local_key`/`thread_local_dtor` modules to the `thread_local` module in `sys` and merged them into a new structure, so that future porters of `std` can simply mix-and-match the existing code instead of having to copy the same (bad) implementation everywhere. The new structure should become obvious when looking at `sys/thread_local/mod.rs`.
Unfortunately, the documentation changes associated with the refactoring have made this PR rather large. That said, this contains no functional changes except for two small ones:
* the key-based destructor fallback now, by virtue of sharing the implementation used by macOS and others, stores its list in a `#[thread_local]` static instead of in the key, eliminating one indirection layer and drastically simplifying its code.
* I've switched over ZKVM (tier 3) to use the same implementation as WebAssembly, as the implementation was just a way worse version of that
Please let me know if I can make this easier to review! I know these large PRs aren't optimal, but I couldn't think of any good intermediate steps.
@rustbot label +A-thread-locals
If we're comfortable using `_NSGetEnviron` from `crt_externs.h`, there shouldn't be an issue with using these either, and then we can merge with the macOS implementation.
This also fixes two test cases on Mac Catalyst:
- `tests/ui/command/command-argv0.rs`, maybe because `[[NSProcessInfo processInfo] arguments]` somehow converts the name of the first argument?
- `tests/ui/env-funky-keys.rs` since we no longer link to Foundation.
Change `SIGPIPE` ui from `#[unix_sigpipe = "..."]` to `-Zon-broken-pipe=...`
In the stabilization [attempt](https://github.com/rust-lang/rust/pull/120832) of `#[unix_sigpipe = "sig_dfl"]`, a concern was [raised ](https://github.com/rust-lang/rust/pull/120832#issuecomment-2007394609) related to using a language attribute for the feature: Long term, we want `fn lang_start()` to be definable by any crate, not just libstd. Having a special language attribute in that case becomes awkward.
So as a first step towards the next stabilization attempt, this PR changes the `#[unix_sigpipe = "..."]` attribute to a compiler flag `-Zon-broken-pipe=...` to remove that concern, since now the language is not "contaminated" by this feature.
Another point was [also raised](https://github.com/rust-lang/rust/pull/120832#issuecomment-1987023484), namely that the ui should not leak **how** it does things, but rather what the **end effect** is. The new flag uses the proposed naming. This is of course something that can be iterated on further before stabilization.
Tracking issue: https://github.com/rust-lang/rust/issues/97889
In the stabilization attempt of `#[unix_sigpipe = "sig_dfl"]`, a concern
was raised related to using a language attribute for the feature: Long
term, we want `fn lang_start()` to be definable by any crate, not just
libstd. Having a special language attribute in that case becomes
awkward.
So as a first step towards towards the next stabilization attempt, this
PR changes the `#[unix_sigpipe = "..."]` attribute to a compiler flag
`-Zon-broken-pipe=...` to remove that concern, since now the language
is not "contaminated" by this feature.
Another point was also raised, namely that the ui should not leak
**how** it does things, but rather what the **end effect** is. The new
flag uses the proposed naming. This is of course something that can be
iterated on further before stabilization.
Delete architecture-specific memchr code in std::sys
Currently all architecture-specific memchr code is only used in `std::io`. Most of the actual `memchr` capacity exposed to the user through the slice API is instead implemented in `core::slice::memchr`.
Hence this commit deletes `memchr` from `std::sys[_common]` and replace calls to it by calls to `core::slice::memchr` functions. This deletes `(r)memchr` from the list of symbols linked to libc.
The interest of putting architecture specific code back in core is linked to the discussion to be had in #113654
Currently all architecture-specific memchr code is only used in
`std::io`. Most of the actual `memchr` capacity exposed to the user
through the slice API is instead implemented in core::slice::memchr.
Hence this commit deletes memchr from std::sys[_common] and replace
calls to it by calls to core::slice::memchr functions. This deletes
(r)memchr from the list of symbols linked to libc.
