From 0a08841bb075959874e2e29c538150c826a1401a Mon Sep 17 00:00:00 2001
From: Simon Sapin <simon.sapin@exyr.org>
Date: Wed, 3 Jul 2019 12:23:26 +0200
Subject: Remove uses of `allow(unions_with_drop_fields)` in the standard
 library

---
 src/libstd/panicking.rs | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

(limited to 'src/libstd')

diff --git a/src/libstd/panicking.rs b/src/libstd/panicking.rs
index 638ce1679b8..296f2a59bb8 100644
--- a/src/libstd/panicking.rs
+++ b/src/libstd/panicking.rs
@@ -12,7 +12,7 @@ use core::panic::{BoxMeUp, PanicInfo, Location};
 use crate::any::Any;
 use crate::fmt;
 use crate::intrinsics;
-use crate::mem;
+use crate::mem::{self, ManuallyDrop};
 use crate::ptr;
 use crate::raw;
 use crate::sync::atomic::{AtomicBool, Ordering};
@@ -227,10 +227,9 @@ pub use realstd::rt::update_panic_count;
 
 /// Invoke a closure, capturing the cause of an unwinding panic if one occurs.
 pub unsafe fn r#try<R, F: FnOnce() -> R>(f: F) -> Result<R, Box<dyn Any + Send>> {
-    #[allow(unions_with_drop_fields)]
     union Data<F, R> {
-        f: F,
-        r: R,
+        f: ManuallyDrop<F>,
+        r: ManuallyDrop<R>,
     }
 
     // We do some sketchy operations with ownership here for the sake of
@@ -261,7 +260,7 @@ pub unsafe fn r#try<R, F: FnOnce() -> R>(f: F) -> Result<R, Box<dyn Any + Send>>
     let mut any_data = 0;
     let mut any_vtable = 0;
     let mut data = Data {
-        f,
+        f: ManuallyDrop::new(f)
     };
 
     let r = __rust_maybe_catch_panic(do_call::<F, R>,
@@ -271,7 +270,7 @@ pub unsafe fn r#try<R, F: FnOnce() -> R>(f: F) -> Result<R, Box<dyn Any + Send>>
 
     return if r == 0 {
         debug_assert!(update_panic_count(0) == 0);
-        Ok(data.r)
+        Ok(ManuallyDrop::into_inner(data.r))
     } else {
         update_panic_count(-1);
         debug_assert!(update_panic_count(0) == 0);
@@ -284,8 +283,8 @@ pub unsafe fn r#try<R, F: FnOnce() -> R>(f: F) -> Result<R, Box<dyn Any + Send>>
     fn do_call<F: FnOnce() -> R, R>(data: *mut u8) {
         unsafe {
             let data = data as *mut Data<F, R>;
-            let f = ptr::read(&mut (*data).f);
-            ptr::write(&mut (*data).r, f());
+            let f = ptr::read(&mut *(*data).f);
+            ptr::write(&mut *(*data).r, f());
         }
     }
 }
-- 
cgit 1.4.1-3-g733a5


From 2fc257ca8144ad6a41b053a01f977afce7a23c95 Mon Sep 17 00:00:00 2001
From: Oliver Scherer <github35764891676564198441@oli-obk.de>
Date: Fri, 20 Sep 2019 12:40:57 +0200
Subject: Prefer `ManuallyDrop::{take,new}` over `ptr::{read,write}`

---
 src/libstd/lib.rs       | 1 +
 src/libstd/panicking.rs | 6 +++---
 2 files changed, 4 insertions(+), 3 deletions(-)

(limited to 'src/libstd')

diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
index 5ff32d7adaf..8e3e02586a6 100644
--- a/src/libstd/lib.rs
+++ b/src/libstd/lib.rs
@@ -275,6 +275,7 @@
 #![feature(link_args)]
 #![feature(linkage)]
 #![feature(log_syntax)]
+#![feature(manually_drop_take)]
 #![feature(maybe_uninit_ref)]
 #![feature(maybe_uninit_slice)]
 #![feature(mem_take)]
diff --git a/src/libstd/panicking.rs b/src/libstd/panicking.rs
index 296f2a59bb8..2dde81bb0ec 100644
--- a/src/libstd/panicking.rs
+++ b/src/libstd/panicking.rs
@@ -13,7 +13,6 @@ use crate::any::Any;
 use crate::fmt;
 use crate::intrinsics;
 use crate::mem::{self, ManuallyDrop};
-use crate::ptr;
 use crate::raw;
 use crate::sync::atomic::{AtomicBool, Ordering};
 use crate::sys::stdio::panic_output;
@@ -283,8 +282,9 @@ pub unsafe fn r#try<R, F: FnOnce() -> R>(f: F) -> Result<R, Box<dyn Any + Send>>
     fn do_call<F: FnOnce() -> R, R>(data: *mut u8) {
         unsafe {
             let data = data as *mut Data<F, R>;
-            let f = ptr::read(&mut *(*data).f);
-            ptr::write(&mut *(*data).r, f());
+            let data = &mut (*data);
+            let f = ManuallyDrop::take(&mut data.f);
+            data.r = ManuallyDrop::new(f());
         }
     }
 }
-- 
cgit 1.4.1-3-g733a5