Add SAFETY comments for AsFd implementations on stdin/stdout/stderr

joshtriplett · sunfishcode · commit 905ebc31b151 · 2022-10-03T08:30:58.000-07:00
diff --git a/library/std/src/sys/wasi/stdio.rs b/library/std/src/sys/wasi/stdio.rs
@@ -34,6 +34,7 @@ impl AsFd for Stdin {
 impl<'a> AsFd for io::StdinLock<'a> {
     #[inline]
     fn as_fd(&self) -> BorrowedFd<'_> {
+        // SAFETY: user code should not close stdin out from under the standard library
         unsafe { BorrowedFd::borrow_raw(0) }
     }
 }
@@ -77,6 +78,7 @@ impl AsFd for Stdout {
 impl<'a> AsFd for io::StdoutLock<'a> {
     #[inline]
     fn as_fd(&self) -> BorrowedFd<'_> {
+        // SAFETY: user code should not close stdout out from under the standard library
         unsafe { BorrowedFd::borrow_raw(1) }
     }
 }
@@ -123,6 +125,7 @@ impl AsFd for Stderr {
 impl<'a> AsFd for io::StderrLock<'a> {
     #[inline]
     fn as_fd(&self) -> BorrowedFd<'_> {
+        // SAFETY: user code should not close stderr out from under the standard library
         unsafe { BorrowedFd::borrow_raw(2) }
     }
 }

Original file line number	Diff line number	Diff line change
`@@ -34,6 +34,7 @@ impl AsFd for Stdin {`
`34`	`34`	`impl<'a> AsFd for io::StdinLock<'a> {`
`35`	`35`	`#[inline]`
`36`	`36`	`fn as_fd(&self) -> BorrowedFd<'_> {`
	`37`	`+ // SAFETY: user code should not close stdin out from under the standard library`
`37`	`38`	`unsafe { BorrowedFd::borrow_raw(0) }`
`38`	`39`	`}`
`39`	`40`	`}`
`@@ -77,6 +78,7 @@ impl AsFd for Stdout {`
`77`	`78`	`impl<'a> AsFd for io::StdoutLock<'a> {`
`78`	`79`	`#[inline]`
`79`	`80`	`fn as_fd(&self) -> BorrowedFd<'_> {`
	`81`	`+ // SAFETY: user code should not close stdout out from under the standard library`
`80`	`82`	`unsafe { BorrowedFd::borrow_raw(1) }`
`81`	`83`	`}`
`82`	`84`	`}`
`@@ -123,6 +125,7 @@ impl AsFd for Stderr {`
`123`	`125`	`impl<'a> AsFd for io::StderrLock<'a> {`
`124`	`126`	`#[inline]`
`125`	`127`	`fn as_fd(&self) -> BorrowedFd<'_> {`
	`128`	`+ // SAFETY: user code should not close stderr out from under the standard library`
`126`	`129`	`unsafe { BorrowedFd::borrow_raw(2) }`
`127`	`130`	`}`
`128`	`131`	`}`