Add comments for #[no_sanitize(cfi)] in stdlib

Author: 1c3t3a

Diff for: library/std/src/sys/fs/unix.rs

@@ -1454,6 +1454,8 @@ impl File {
         Ok(())
     }
 
+    // FIXME(#115199): Rust currently omits weak function definitions
+    // and its metadata from LLVM IR.
     #[cfg_attr(
         any(
             target_os = "android",

Diff for: library/std/src/sys/pal/unix/fd.rs

@@ -251,6 +251,8 @@ impl FileDesc {
     }
 
     #[cfg(all(target_os = "android", target_pointer_width = "32"))]
+    // FIXME(#115199): Rust currently omits weak function definitions
+    // and its metadata from LLVM IR.
     #[no_sanitize(cfi)]
     pub fn read_vectored_at(&self, bufs: &mut [IoSliceMut<'_>], offset: u64) -> io::Result<usize> {
         super::weak::weak!(fn preadv64(libc::c_int, *const libc::iovec, libc::c_int, off64_t) -> isize);

Diff for: library/std/src/sys/pal/unix/process/process_unix.rs

@@ -434,6 +434,8 @@ impl Command {
         target_os = "nto",
         target_vendor = "apple",
     ))]
+    // FIXME(#115199): Rust currently omits weak function definitions
+    // and its metadata from LLVM IR.
     #[cfg_attr(target_os = "linux", no_sanitize(cfi))]
     fn posix_spawn(
         &mut self,

Diff for: library/std/src/sys/pal/unix/thread.rs

@@ -188,6 +188,8 @@ impl Thread {
     }
 
     #[cfg(any(target_os = "solaris", target_os = "illumos", target_os = "nto"))]
+    // FIXME(#115199): Rust currently omits weak function definitions
+    // and its metadata from LLVM IR.
     #[no_sanitize(cfi)]
     pub fn set_name(name: &CStr) {
         weak! {

Diff for: library/std/src/sys/pal/unix/time.rs

@@ -96,6 +96,8 @@ impl Timespec {
         }
     }
 
+    // FIXME(#115199): Rust currently omits weak function definitions
+    // and its metadata from LLVM IR.
     #[cfg_attr(
         all(
             target_os = "linux",

Diff for: library/std/src/sys/pal/unix/weak.rs

@@ -144,7 +144,7 @@ unsafe fn fetch(name: &str) -> *mut libc::c_void {
 #[cfg(not(any(target_os = "linux", target_os = "android")))]
 pub(crate) macro syscall {
     (fn $name:ident($($arg_name:ident: $t:ty),*) -> $ret:ty) => (
-        // FIXME: Rust currently omits weak function definitions
+        // FIXME(#115199): Rust currently omits weak function definitions
         // and its metadata from LLVM IR.
         #[no_sanitize(cfi)]
         unsafe fn $name($($arg_name: $t),*) -> $ret {