Auto merge of #73265 - mark-i-m:mv-std, r=<try>tmp-nightly

mv std libs to library/

This is the first step in refactoring the directory layout of this repository, with further followup steps planned (but not done yet).

Background: currently, all crates are under src/, without nested src directories and with the unconventional `lib*` prefixes (e.g., `src/libcore/lib.rs`). This directory structures is not idiomatic and makes the `src/` directory rather overwhelming. To improve contributor experience and make things a bit more approachable, we are reorganizing the repo a bit.

In this PR, we move the standard libs (basically anything that is "runtime", as opposed to part of the compiler, build system, or one of the tools, etc). The new layout moves these libraries to a new `library/` directory in the root of the repo. Additionally, we remove the `lib*` prefixes and add nested `src/` directories.  The other crates/tools in this repo are not touched. So in summary:

```
library/<crate>/src/*.rs
src/<all the rest>     // unchanged
```

where `<crate>` is:
- core
- alloc
- std
- test
- proc_macro
- panic_abort
- panic_unwind
- profiler_builtins
- term
- unwind
- rtstartup
- backtrace
- rustc-std-workspace-*

There was a lot of discussion about this and a few rounds of compiler team approvals, FCPs, MCPs, and nominations. The original MCP is https://github.com/rust-lang/compiler-team/issues/298. The final approval of the compiler team was given here: https://github.com/rust-lang/rust/pull/73265#issuecomment-659498446.

The name `library` was chosen to complement a later move of the compiler crates to a `compiler/` directory. There was a lot of discussion around adding the nested `src/` directories. Note that this does increase the nesting depth (plausibly important for manual traversal of the tree, e.g., through GitHub's UI or `cd`), but this is deemed to be better as it fits the standard layout of Rust crates throughout most of the ecosystem, though there is some debate about how much this should apply to multi-crate projects. Overall, there seem to be more people in favor of nested `src/` than against.

After this PR, there are no dependencies out of the `library/` directory except on the `build_helper` (or crates.io crates).

1 files changed, 0 insertions, 68 deletions

diff --git a/src/libstd/rt.rs b/src/libstd/rt.rs
deleted file mode 100644
index fb825ab16eb..00000000000
--- a/src/libstd/rt.rs
+++ /dev/null
@@ -1,68 +0,0 @@
-//! Runtime services
-//!
-//! The `rt` module provides a narrow set of runtime services,
-//! including the global heap (exported in `heap`) and unwinding and
-//! backtrace support. The APIs in this module are highly unstable,
-//! and should be considered as private implementation details for the
-//! time being.
-
-#![unstable(
-    feature = "rt",
-    reason = "this public module should not exist and is highly likely \
-              to disappear",
-    issue = "none"
-)]
-#![doc(hidden)]
-
-// Re-export some of our utilities which are expected by other crates.
-pub use crate::panicking::{begin_panic, begin_panic_fmt, panic_count};
-
-// To reduce the generated code of the new `lang_start`, this function is doing
-// the real work.
-#[cfg(not(test))]
-fn lang_start_internal(
-    main: &(dyn Fn() -> i32 + Sync + crate::panic::RefUnwindSafe),
-    argc: isize,
-    argv: *const *const u8,
-) -> isize {
-    use crate::panic;
-    use crate::sys;
-    use crate::sys_common;
-    use crate::sys_common::thread_info;
-    use crate::thread::Thread;
-
-    sys::init();
-
-    unsafe {
-        let main_guard = sys::thread::guard::init();
-        sys::stack_overflow::init();
-
-        // Next, set up the current Thread with the guard information we just
-        // created. Note that this isn't necessary in general for new threads,
-        // but we just do this to name the main thread and to give it correct
-        // info about the stack bounds.
-        let thread = Thread::new(Some("main".to_owned()));
-        thread_info::set(main_guard, thread);
-
-        // Store our args if necessary in a squirreled away location
-        sys::args::init(argc, argv);
-
-        // Let's run some code!
-        let exit_code = panic::catch_unwind(|| {
-            sys_common::backtrace::__rust_begin_short_backtrace(move || main())
-        });
-
-        sys_common::cleanup();
-        exit_code.unwrap_or(101) as isize
-    }
-}
-
-#[cfg(not(test))]
-#[lang = "start"]
-fn lang_start<T: crate::process::Termination + 'static>(
-    main: fn() -> T,
-    argc: isize,
-    argv: *const *const u8,
-) -> isize {
-    lang_start_internal(&move || main().report(), argc, argv)
-}