Auto merge of #73265 - mark-i-m:mv-std, r=Mark-Simulacrum,mark-i-m

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, 167 deletions

diff --git a/src/libstd/sys/unix/android.rs b/src/libstd/sys/unix/android.rs
deleted file mode 100644
index ea05ee3d7ce..00000000000
--- a/src/libstd/sys/unix/android.rs
+++ /dev/null
@@ -1,167 +0,0 @@
-//! Android ABI-compatibility module
-//!
-//! The ABI of Android has changed quite a bit over time, and libstd attempts to
-//! be both forwards and backwards compatible as much as possible. We want to
-//! always work with the most recent version of Android, but we also want to
-//! work with older versions of Android for whenever projects need to.
-//!
-//! Our current minimum supported Android version is `android-9`, e.g., Android
-//! with API level 9. We then in theory want to work on that and all future
-//! versions of Android!
-//!
-//! Some of the detection here is done at runtime via `dlopen` and
-//! introspection. Other times no detection is performed at all and we just
-//! provide a fallback implementation as some versions of Android we support
-//! don't have the function.
-//!
-//! You'll find more details below about why each compatibility shim is needed.
-
-#![cfg(target_os = "android")]
-
-use libc::{c_int, c_void, sighandler_t, size_t, ssize_t};
-use libc::{ftruncate, pread, pwrite};
-
-use super::{cvt, cvt_r};
-use crate::io;
-
-// The `log2` and `log2f` functions apparently appeared in android-18, or at
-// least you can see they're not present in the android-17 header [1] and they
-// are present in android-18 [2].
-//
-// [1]: https://chromium.googlesource.com/android_tools/+/20ee6d20/ndk/platforms
-//                                       /android-17/arch-arm/usr/include/math.h
-// [2]: https://chromium.googlesource.com/android_tools/+/20ee6d20/ndk/platforms
-//                                       /android-18/arch-arm/usr/include/math.h
-//
-// Note that these shims are likely less precise than directly calling `log2`,
-// but hopefully that should be enough for now...
-//
-// Note that mathematically, for any arbitrary `y`:
-//
-//      log_2(x) = log_y(x) / log_y(2)
-//               = log_y(x) / (1 / log_2(y))
-//               = log_y(x) * log_2(y)
-//
-// Hence because `ln` (log_e) is available on all Android we just choose `y = e`
-// and get:
-//
-//      log_2(x) = ln(x) * log_2(e)
-
-#[cfg(not(test))]
-pub fn log2f32(f: f32) -> f32 {
-    f.ln() * crate::f32::consts::LOG2_E
-}
-
-#[cfg(not(test))]
-pub fn log2f64(f: f64) -> f64 {
-    f.ln() * crate::f64::consts::LOG2_E
-}
-
-// Back in the day [1] the `signal` function was just an inline wrapper
-// around `bsd_signal`, but starting in API level android-20 the `signal`
-// symbols was introduced [2]. Finally, in android-21 the API `bsd_signal` was
-// removed [3].
-//
-// Basically this means that if we want to be binary compatible with multiple
-// Android releases (oldest being 9 and newest being 21) then we need to check
-// for both symbols and not actually link against either.
-//
-// [1]: https://chromium.googlesource.com/android_tools/+/20ee6d20/ndk/platforms
-//                                       /android-18/arch-arm/usr/include/signal.h
-// [2]: https://chromium.googlesource.com/android_tools/+/fbd420/ndk_experimental
-//                                       /platforms/android-20/arch-arm
-//                                       /usr/include/signal.h
-// [3]: https://chromium.googlesource.com/android_tools/+/20ee6d/ndk/platforms
-//                                       /android-21/arch-arm/usr/include/signal.h
-pub unsafe fn signal(signum: c_int, handler: sighandler_t) -> sighandler_t {
-    weak!(fn signal(c_int, sighandler_t) -> sighandler_t);
-    weak!(fn bsd_signal(c_int, sighandler_t) -> sighandler_t);
-
-    let f = signal.get().or_else(|| bsd_signal.get());
-    let f = f.expect("neither `signal` nor `bsd_signal` symbols found");
-    f(signum, handler)
-}
-
-// The `ftruncate64` symbol apparently appeared in android-12, so we do some
-// dynamic detection to see if we can figure out whether `ftruncate64` exists.
-//
-// If it doesn't we just fall back to `ftruncate`, generating an error for
-// too-large values.
-#[cfg(target_pointer_width = "32")]
-pub fn ftruncate64(fd: c_int, size: u64) -> io::Result<()> {
-    weak!(fn ftruncate64(c_int, i64) -> c_int);
-
-    unsafe {
-        match ftruncate64.get() {
-            Some(f) => cvt_r(|| f(fd, size as i64)).map(drop),
-            None => {
-                if size > i32::MAX as u64 {
-                    Err(io::Error::new(io::ErrorKind::InvalidInput, "cannot truncate >2GB"))
-                } else {
-                    cvt_r(|| ftruncate(fd, size as i32)).map(drop)
-                }
-            }
-        }
-    }
-}
-
-#[cfg(target_pointer_width = "64")]
-pub fn ftruncate64(fd: c_int, size: u64) -> io::Result<()> {
-    unsafe { cvt_r(|| ftruncate(fd, size as i64)).map(drop) }
-}
-
-#[cfg(target_pointer_width = "32")]
-pub unsafe fn cvt_pread64(
-    fd: c_int,
-    buf: *mut c_void,
-    count: size_t,
-    offset: i64,
-) -> io::Result<ssize_t> {
-    use crate::convert::TryInto;
-    weak!(fn pread64(c_int, *mut c_void, size_t, i64) -> ssize_t);
-    pread64.get().map(|f| cvt(f(fd, buf, count, offset))).unwrap_or_else(|| {
-        if let Ok(o) = offset.try_into() {
-            cvt(pread(fd, buf, count, o))
-        } else {
-            Err(io::Error::new(io::ErrorKind::InvalidInput, "cannot pread >2GB"))
-        }
-    })
-}
-
-#[cfg(target_pointer_width = "32")]
-pub unsafe fn cvt_pwrite64(
-    fd: c_int,
-    buf: *const c_void,
-    count: size_t,
-    offset: i64,
-) -> io::Result<ssize_t> {
-    use crate::convert::TryInto;
-    weak!(fn pwrite64(c_int, *const c_void, size_t, i64) -> ssize_t);
-    pwrite64.get().map(|f| cvt(f(fd, buf, count, offset))).unwrap_or_else(|| {
-        if let Ok(o) = offset.try_into() {
-            cvt(pwrite(fd, buf, count, o))
-        } else {
-            Err(io::Error::new(io::ErrorKind::InvalidInput, "cannot pwrite >2GB"))
-        }
-    })
-}
-
-#[cfg(target_pointer_width = "64")]
-pub unsafe fn cvt_pread64(
-    fd: c_int,
-    buf: *mut c_void,
-    count: size_t,
-    offset: i64,
-) -> io::Result<ssize_t> {
-    cvt(pread(fd, buf, count, offset))
-}
-
-#[cfg(target_pointer_width = "64")]
-pub unsafe fn cvt_pwrite64(
-    fd: c_int,
-    buf: *const c_void,
-    count: size_t,
-    offset: i64,
-) -> io::Result<ssize_t> {
-    cvt(pwrite(fd, buf, count, offset))
-}