Solve stdin/out/err UB in a better way

Cargo.lock

@@ -80,6 +80,7 @@ name = "crt0"
 version = "0.1.0"
 dependencies = [
  "platform 0.1.0",
+ "stdio 0.1.0",
 ]
 
 [[package]]

include/bits/stdio.h

@@ -3,9 +3,6 @@
 
 #define EOF (-1)
 #define BUFSIZ 1024
-#define stdin __stdin()
-#define stdout __stdout()
-#define stderr __stderr()
 
 int fprintf(FILE * stream, const char * fmt, ...);
 int printf(const char * fmt, ...);

src/crt0/Cargo.toml

@@ -9,3 +9,4 @@ crate-type = ["staticlib"]
 
 [dependencies]
 platform = { path = "../platform" }
+stdio = { path = "../stdio" }

src/crt0/src/lib.rs

@@ -10,6 +10,7 @@
 
 extern crate alloc;
 extern crate platform;
+extern crate stdio;
 
 use alloc::Vec;
 use core::ptr;
@@ -89,6 +90,11 @@ pub unsafe extern "C" fn _start_rust(sp: &'static Stack) -> ! {
     platform::inner_environ.push(ptr::null_mut());
     platform::environ = platform::inner_environ.as_mut_ptr();
 
+    // Initialize stdin/stdout/stderr, see https://github.com/rust-lang/rust/issues/51718
+    stdio::stdin = stdio::default_stdin.get();
+    stdio::stdout = stdio::default_stdout.get();
+    stdio::stderr = stdio::default_stderr.get();
+
     platform::exit(main(
         argc,
         argv as *const *const c_char,

src/stdio/src/default.rs

@@ -1,37 +1,23 @@
 use super::{constants, BUFSIZ, FILE, UNGET};
 use core::cell::UnsafeCell;
+use core::ptr;
 use core::sync::atomic::AtomicBool;
 
-struct GlobalFile(UnsafeCell<FILE>);
+pub struct GlobalFile(UnsafeCell<FILE>);
 impl GlobalFile {
     const fn new(file: FILE) -> Self {
         GlobalFile(UnsafeCell::new(file))
     }
-    fn get(&self) -> *mut FILE {
+    pub 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 {
-    default_stdin.get()
-}
-
-#[no_mangle]
-pub extern "C" fn __stdout() -> *mut FILE {
-    default_stdout.get()
-}
-
-#[no_mangle]
-pub extern "C" fn __stderr() -> *mut FILE {
-    default_stderr.get()
-}
-
 lazy_static! {
     #[allow(non_upper_case_globals)]
-    static ref default_stdin: GlobalFile = GlobalFile::new(FILE {
+    pub static ref default_stdin: GlobalFile = GlobalFile::new(FILE {
         flags: constants::F_PERM | constants::F_NOWR,
         read: None,
         write: None,
@@ -43,7 +29,7 @@ lazy_static! {
     });
 
     #[allow(non_upper_case_globals)]
-    static ref default_stdout: GlobalFile = GlobalFile::new(FILE {
+    pub static ref default_stdout: GlobalFile = GlobalFile::new(FILE {
         flags: constants::F_PERM | constants::F_NORD,
         read: None,
         write: None,
@@ -55,7 +41,7 @@ lazy_static! {
     });
 
     #[allow(non_upper_case_globals)]
-    static ref default_stderr: GlobalFile = GlobalFile::new(FILE {
+    pub static ref default_stderr: GlobalFile = GlobalFile::new(FILE {
         flags: constants::F_PERM | constants::F_NORD,
         read: None,
         write: None,
@@ -66,3 +52,10 @@ lazy_static! {
         lock: AtomicBool::new(false),
     });
 }
+
+#[no_mangle]
+pub static mut stdin: *mut FILE = ptr::null_mut();
+#[no_mangle]
+pub static mut stdout: *mut FILE = ptr::null_mut();
+#[no_mangle]
+pub static mut stderr: *mut FILE = ptr::null_mut();

src/stdio/src/lib.rs

@@ -643,7 +643,7 @@ pub extern "C" fn getc(stream: &mut FILE) -> c_int {
 /// Get a single char from `stdin`
 #[no_mangle]
 pub extern "C" fn getchar() -> c_int {
-    fgetc(unsafe { &mut *__stdin() })
+    fgetc(unsafe { &mut *stdin })
 }
 
 /// Get a char from a stream without locking the stream
@@ -676,14 +676,14 @@ pub extern "C" fn getc_unlocked(stream: &mut FILE) -> c_int {
 /// Get a char from `stdin` without locking `stdin`
 #[no_mangle]
 pub extern "C" fn getchar_unlocked() -> c_int {
-    getc_unlocked(unsafe { &mut *__stdin() })
+    getc_unlocked(unsafe { &mut *stdin })
 }
 
 /// Get a string from `stdin`
 #[no_mangle]
 pub extern "C" fn gets(s: *mut c_char) -> *mut c_char {
     use core::i32;
-    fgets(s, i32::MAX, unsafe { &mut *__stdin() })
+    fgets(s, i32::MAX, unsafe { &mut *stdin })
 }
 
 /// Get an integer from `stream`
@@ -740,7 +740,7 @@ pub extern "C" fn putc(c: c_int, stream: &mut FILE) -> c_int {
 /// Put a character `c` into `stdout`
 #[no_mangle]
 pub extern "C" fn putchar(c: c_int) -> c_int {
-    fputc(c, unsafe { &mut *__stdout() })
+    fputc(c, unsafe { &mut *stdout })
 }
 
 /// Put a character `c` into `stream` without locking `stream`
@@ -768,13 +768,13 @@ pub extern "C" fn putc_unlocked(c: c_int, stream: &mut FILE) -> c_int {
 /// Put a character `c` into `stdout` without locking `stdout`
 #[no_mangle]
 pub extern "C" fn putchar_unlocked(c: c_int) -> c_int {
-    putc_unlocked(c, unsafe { &mut *__stdout() })
+    putc_unlocked(c, unsafe { &mut *stdout })
 }
 
 /// Put a string `s` into `stdout`
 #[no_mangle]
 pub extern "C" fn puts(s: *const c_char) -> c_int {
-    let ret = (fputs(s, unsafe { &mut *__stdout() }) > 0) || (putchar_unlocked(b'\n' as c_int) > 0);
+    let ret = (fputs(s, unsafe { &mut *stdout }) > 0) || (putchar_unlocked(b'\n' as c_int) > 0);
     if ret {
         0
     } else {
@@ -918,7 +918,7 @@ pub unsafe extern "C" fn vfprintf(file: &mut FILE, format: *const c_char, ap: va
 
 #[no_mangle]
 pub unsafe extern "C" fn vprintf(format: *const c_char, ap: va_list) -> c_int {
-    vfprintf(&mut *__stdout(), format, ap)
+    vfprintf(&mut *stdout, format, ap)
 }
 
 #[no_mangle]
@@ -947,7 +947,7 @@ pub unsafe extern "C" fn vfscanf(file: &mut FILE, format: *const c_char, ap: va_
 
 #[no_mangle]
 pub unsafe extern "C" fn vscanf(format: *const c_char, ap: va_list) -> c_int {
-    vfscanf(&mut *__stdin(), format, ap)
+    vfscanf(&mut *stdin, format, ap)
 }
 
 #[no_mangle]

src/unistd/src/getopt.rs

@@ -70,10 +70,10 @@ unsafe fn parse_arg(
 
     let print_error = |desc: &[u8]| {
         // NOTE: we don't use fprintf to get around the usage of va_list
-        stdio::fputs(*argv as _, &mut *stdio::__stderr());
-        stdio::fputs(desc.as_ptr() as _, &mut *stdio::__stderr());
-        stdio::fputc(*current_arg as _, &mut *stdio::__stderr());
-        stdio::fputc(b'\n' as _, &mut *stdio::__stderr());
+        stdio::fputs(*argv as _, &mut *stdio::stderr);
+        stdio::fputs(desc.as_ptr() as _, &mut *stdio::stderr);
+        stdio::fputc(*current_arg as _, &mut *stdio::stderr);
+        stdio::fputc(b'\n' as _, &mut *stdio::stderr);
     };
 
     match find_option(*current_arg, optstring) {

src/wchar/src/lib.rs

@@ -203,7 +203,7 @@ pub unsafe extern "C" fn putwc(wc: wchar_t, stream: *mut FILE) -> wint_t {
 
 #[no_mangle]
 pub unsafe extern "C" fn putwchar(wc: wchar_t) -> wint_t {
-    fputwc(wc, &mut *__stdout())
+    fputwc(wc, &mut *stdout)
 }
 
 // #[no_mangle]

tests/expected/unistd/stat.stdout

@@ -1,4 +0,0 @@
-144
-st_mode: 33188
-st_size: 383
-st_blksize: 4096