Changed FILE to use a vector as a buffer instead of raw pointers. This allows us to remove the large majority of unsafe blocks from the code

src/stdio/src/default.rs

@@ -39,6 +39,18 @@ lazy_static! {
     };
 }
 
+struct GlobalFile(UnsafeCell<FILE>);
+impl GlobalFile {
+    const fn new(file: FILE) -> Self {
+        GlobalFile(UnsafeCell::new(file))
+    }
+    fn get(&self) -> *mut FILE {
+        self.0.get()
+    }
+}
+// statics need to be Sync
+unsafe impl Sync for GlobalFile {}
+
 #[no_mangle]
 pub extern "C" fn __stdin() -> *mut FILE {
     unsafe { &mut default_stdin }
@@ -53,3 +65,41 @@ pub extern "C" fn __stdout() -> *mut FILE {
 pub extern "C" fn __stderr() -> *mut FILE {
     unsafe { &mut default_stderr }
 }
+
+lazy_static! {
+    #[allow(non_upper_case_globals)]
+    static ref default_stdin: GlobalFile = GlobalFile::new(FILE {
+        flags: constants::F_PERM | constants::F_NOWR,
+        read: None,
+        write: None,
+        fd: 0,
+        buf: vec![0u8;(BUFSIZ + UNGET) as usize],
+        buf_char: -1,
+        unget: UNGET,
+        lock: AtomicBool::new(false),
+    });
+
+    #[allow(non_upper_case_globals)]
+    static ref default_stdout: GlobalFile = GlobalFile::new(FILE {
+        flags: constants::F_PERM | constants::F_NORD,
+        read: None,
+        write: None,
+        fd: 1,
+        buf: vec![0u8;(BUFSIZ + UNGET) as usize],
+        buf_char: b'\n' as i8,
+        unget: 0,
+        lock: AtomicBool::new(false),
+    });
+
+    #[allow(non_upper_case_globals)]
+    static ref default_stderr: GlobalFile = GlobalFile::new(FILE {
+        flags: constants::F_PERM | constants::F_NORD,
+        read: None,
+        write: None,
+        fd: 2,
+        buf: vec![0u8;(BUFSIZ + UNGET) as usize],
+        buf_char: -1,
+        unget: 0,
+        lock: AtomicBool::new(false),
+    });
+}