Fallbacks for CreateSymbolicLinkW, CreateHardLinkW, GetFinalPathNameByHandleW

- `CreateSymbolicLinkW` is used in `std::fs::soft_link`. Fails on unsupported systems.
- `CreateHardLinkW` is used in `std::fs::hard_link`. Fails on unsupported systems.
- `GetFinalPathNameByHandleW` is used in `std::fs::canonicalize`. Systems that don't support `GetFinalPathNameByHandleW` also don't support symlinks, so the fallback uses `GetFullPathNameW` instead.

Author: seritools

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

@@ -445,3 +445,38 @@ compat_fn_with_fallback! {
         FALSE
     }
 }
+
+#[cfg(target_vendor = "rust9x")]
+compat_fn_with_fallback! {
+    pub static KERNEL32: &CStr = c"kernel32" => { load: false, unicows: false };
+    // >= Vista / Server 2008
+    // https://learn.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-createsymboliclinkw
+    pub fn CreateSymbolicLinkW(
+        lpsymlinkfilename: PCWSTR,
+        lptargetfilename: PCWSTR,
+        dwflags: SYMBOLIC_LINK_FLAGS,
+    ) -> BOOLEAN {
+        unsafe { SetLastError(ERROR_CALL_NOT_IMPLEMENTED as u32); };
+        0
+    }
+    // >= Vista / Server 2008
+    // https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-getfinalpathnamebyhandlew
+    pub fn GetFinalPathNameByHandleW(
+        hfile: HANDLE,
+        lpszfilepath: PWSTR,
+        cchfilepath: u32,
+        dwflags: GETFINALPATHNAMEBYHANDLE_FLAGS
+    ) -> u32 {
+        rtabort!("unimplemented")
+    }
+    // >= 2000
+    // https://learn.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-createhardlinkw
+    pub fn CreateHardLinkW(
+        lpfilename: PCWSTR,
+        lpexistingfilename: PCWSTR,
+        lpsecurityattributes: *const SECURITY_ATTRIBUTES,
+    ) -> BOOL {
+        unsafe { SetLastError(ERROR_CALL_NOT_IMPLEMENTED as u32); };
+        FALSE
+    }
+}

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

@@ -1526,6 +1526,7 @@ fn get_path(f: &File) -> io::Result<PathBuf> {
     )
 }
 
+#[cfg(not(target_vendor = "rust9x"))]
 pub fn canonicalize(p: &Path) -> io::Result<PathBuf> {
     let mut opts = OpenOptions::new();
     // No read or write permissions are necessary
@@ -1536,6 +1537,28 @@ pub fn canonicalize(p: &Path) -> io::Result<PathBuf> {
     get_path(&f)
 }
 
+#[cfg(target_vendor = "rust9x")]
+pub fn canonicalize(p: &Path) -> io::Result<PathBuf> {
+    if c::GetFinalPathNameByHandleW::available().is_some() {
+        let mut opts = OpenOptions::new();
+        // No read or write permissions are necessary
+        opts.access_mode(0);
+        // This flag is so we can open directories too
+        opts.custom_flags(c::FILE_FLAG_BACKUP_SEMANTICS);
+        let f = File::open(p, &opts)?;
+        get_path(&f)
+    } else {
+        // systems that don't support GetFinalPathNameByHandleW also don't support symlinks, so we
+        // fall back to using GetFullPathName.
+        let path = maybe_verbatim(p)?;
+        let mut file_part = ptr::null_mut();
+        super::fill_utf16_buf(
+            |buf, sz| unsafe { c::GetFullPathNameW(path.as_ptr(), sz, buf, &mut file_part) },
+            |buf| PathBuf::from(OsString::from_wide(buf)),
+        )
+    }
+}
+
 pub fn copy(from: &Path, to: &Path) -> io::Result<u64> {
     unsafe extern "system" fn callback(
         _TotalFileSize: i64,