Rollup merge of #134996 - bdbai:uwp-support, r=jieyouxu,ChrisDenton

Add UWP (msvc) target support page

- Added Platform Support page for `x86_64-uwp-windows-msvc`, `i686-uwp-windows-msvc`, `thumbv7a-uwp-windows-msvc` and `aarch64-uwp-windows-msvc`
  - Adding myself as a maintainer
  - Removing the ticks for `thumbv7a-pc-windows-msvc` and `thumbv7a-uwp-windows-msvc` as they do not currently build due to #134565 and https://github.com/rust-lang/backtrace-rs/pull/685
- Fixed a few minor issues to let most of the UWP targets compile
- Happy new year to all!

r? jieyouxu

library/std/src/sys/pal/windows/os.rs

@@ -5,8 +5,9 @@
 #[cfg(test)]
 mod tests;
 
-use super::api::{self, WinError};
-use super::to_u16s;
+#[cfg(not(target_vendor = "uwp"))]
+use super::api::WinError;
+use super::{api, to_u16s};
 use crate::error::Error as StdError;
 use crate::ffi::{OsStr, OsString};
 use crate::os::windows::ffi::EncodeWide;

src/doc/rustc/src/SUMMARY.md

@@ -87,6 +87,7 @@
     - [*-unknown-openbsd](platform-support/openbsd.md)
     - [*-unknown-redox](platform-support/redox.md)
     - [\*-unknown-uefi](platform-support/unknown-uefi.md)
+    - [\*-uwp-windows-msvc](platform-support/uwp-windows-msvc.md)
     - [\*-wrs-vxworks](platform-support/vxworks.md)
     - [wasm32-wasip1](platform-support/wasm32-wasip1.md)
     - [wasm32-wasip1-threads](platform-support/wasm32-wasip1-threads.md)

src/doc/rustc/src/platform-support.md

@@ -264,7 +264,7 @@ target | std | host | notes
 [`aarch64-unknown-redox`](platform-support/redox.md) | ✓ |  | ARM64 Redox OS
 [`aarch64-unknown-teeos`](platform-support/aarch64-unknown-teeos.md) | ? |  | ARM64 TEEOS |
 [`aarch64-unknown-trusty`](platform-support/trusty.md) | ? |  |
-`aarch64-uwp-windows-msvc` | ✓ |  |
+[`aarch64-uwp-windows-msvc`](platform-support/uwp-windows-msvc.md) | ✓ |  |
 [`aarch64-wrs-vxworks`](platform-support/vxworks.md) | ✓ |  | ARM64 VxWorks OS
 `aarch64_be-unknown-linux-gnu` | ✓ | ✓ | ARM64 Linux (big-endian)
 `aarch64_be-unknown-linux-gnu_ilp32` | ✓ | ✓ | ARM64 Linux (big-endian, ILP32 ABI)
@@ -312,7 +312,7 @@ target | std | host | notes
 [`i686-unknown-openbsd`](platform-support/openbsd.md) | ✓ | ✓ | 32-bit OpenBSD [^x86_32-floats-return-ABI]
 [`i686-unknown-redox`](platform-support/redox.md) | ✓ |  | i686 Redox OS
 `i686-uwp-windows-gnu` | ✓ |  | [^x86_32-floats-return-ABI]
-`i686-uwp-windows-msvc` | ✓ |  | [^x86_32-floats-return-ABI]
+[`i686-uwp-windows-msvc`](platform-support/uwp-windows-msvc.md) | ✓ |  | [^x86_32-floats-return-ABI]
 [`i686-win7-windows-msvc`](platform-support/win7-windows-msvc.md) | ✓ |   | 32-bit Windows 7 support [^x86_32-floats-return-ABI]
 [`i686-wrs-vxworks`](platform-support/vxworks.md) | ✓ |  | [^x86_32-floats-return-ABI]
 [`loongarch64-unknown-linux-ohos`](platform-support/openharmony.md) | ✓ |   | LoongArch64 OpenHarmony
@@ -383,8 +383,8 @@ target | std | host | notes
 [`thumbv4t-none-eabi`](platform-support/armv4t-none-eabi.md) | * |  | Thumb-mode Bare Armv4T
 [`thumbv5te-none-eabi`](platform-support/armv5te-none-eabi.md) | * |  | Thumb-mode Bare Armv5TE
 [`thumbv6m-nuttx-eabi`](platform-support/nuttx.md) | * |  | ARMv6M with NuttX
-`thumbv7a-pc-windows-msvc` | ✓ |  |
-`thumbv7a-uwp-windows-msvc` | ✓ |  |
+`thumbv7a-pc-windows-msvc` |  |  |
+[`thumbv7a-uwp-windows-msvc`](platform-support/uwp-windows-msvc.md) |  |  |
 [`thumbv7em-nuttx-eabi`](platform-support/nuttx.md) | * |  | ARMv7EM with NuttX
 [`thumbv7em-nuttx-eabihf`](platform-support/nuttx.md) | * |  | ARMv7EM with NuttX, hardfloat
 [`thumbv7m-nuttx-eabi`](platform-support/nuttx.md) | * |  | ARMv7M with NuttX
@@ -406,7 +406,7 @@ target | std | host | notes
 [`x86_64-unknown-openbsd`](platform-support/openbsd.md) | ✓ | ✓ | 64-bit OpenBSD
 [`x86_64-unknown-trusty`](platform-support/trusty.md) | ? |  |
 `x86_64-uwp-windows-gnu` | ✓ |  |
-`x86_64-uwp-windows-msvc` | ✓ |  |
+[`x86_64-uwp-windows-msvc`](platform-support/uwp-windows-msvc.md) | ✓ |  |
 [`x86_64-win7-windows-msvc`](platform-support/win7-windows-msvc.md) | ✓ |   | 64-bit Windows 7 support
 [`x86_64-wrs-vxworks`](platform-support/vxworks.md) | ✓ |  |
 [`x86_64h-apple-darwin`](platform-support/x86_64h-apple-darwin.md) | ✓ | ✓ | macOS with late-gen Intel (at least Haswell)

src/doc/rustc/src/platform-support/uwp-windows-msvc.md

@@ -0,0 +1,52 @@
+# `x86_64-uwp-windows-msvc`, `i686-uwp-windows-msvc`, `thumbv7a-uwp-windows-msvc` and `aarch64-uwp-windows-msvc`
+
+**Tier: 3**
+
+Windows targets for Universal Windows Platform (UWP) applications, using MSVC toolchain.
+
+## Target maintainers
+
+- [@bdbai](https://github.com/bdbai)
+
+## Requirements
+
+These targets are cross-compiled with std support. The host requirement and
+binary format are the same as the corresponding non-UWP targets (i.e.
+`x86_64-pc-windows-msvc`, `i686-pc-windows-msvc`, `thumbv7a-pc-windows-msvc`
+and `aarch64-pc-windows-msvc`).
+
+## Building the targets
+
+The targets can be built by enabling them for a `rustc` build, for example:
+
+```toml
+[build]
+build-stage = 1
+target = ["x86_64-uwp-windows-msvc", "aarch64-uwp-windows-msvc"]
+```
+
+## Building Rust programs
+
+Rust does not yet ship pre-compiled artifacts for these targets. To compile for
+these targets, you will either need to build Rust with the targets enabled (see
+"Building the targets" above), or build your own copy of `std` by using
+`build-std` or similar.
+
+Example of building a Rust project for x64 UWP using `build-std`:
+
+```pwsh
+cargo build -Z build-std=std,panic_abort --target x86_64-uwp-windows-msvc
+```
+
+## Testing
+
+Currently there is no support to run the rustc test suite for this target.
+
+## Cross-compilation toolchains and C code
+
+In general, the toolchain target should match the corresponding non-UWP
+targets. Beware that not all Win32 APIs behave the same way in UWP, and some
+are restricted in [AppContainer](https://learn.microsoft.com/en-us/windows/win32/secauthz/appcontainer-for-legacy-applications-)
+or even not available at all. If the C code being compiled happens to use any
+of restricted or unavailable APIs, consider using allowed alternatives or
+disable certain feature sets to avoid using them.