From 23d3ff1b9756c768c4412dcd1d80cff0617fd5c5 Mon Sep 17 00:00:00 2001
From: Simon Sapin <simon.sapin@exyr.org>
Date: Sun, 6 Oct 2019 23:45:25 +0200
Subject: Fix zero-size uninitialized boxes

Requesting a zero-size allocation is not allowed,
return a dangling pointer instead.

CC https://github.com/rust-lang/rust/issues/63291#issuecomment-538692745
---
 src/liballoc/boxed.rs | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

(limited to 'src/liballoc')

diff --git a/src/liballoc/boxed.rs b/src/liballoc/boxed.rs
index 9b5d9431ae2..2693a64e13b 100644
--- a/src/liballoc/boxed.rs
+++ b/src/liballoc/boxed.rs
@@ -141,6 +141,9 @@ impl<T> Box<T> {
     /// ```
     #[unstable(feature = "new_uninit", issue = "63291")]
     pub fn new_uninit() -> Box<mem::MaybeUninit<T>> {
+        if mem::size_of::<T>() == 0 {
+            return Box(NonNull::dangling().into())
+        }
         let layout = alloc::Layout::new::<mem::MaybeUninit<T>>();
         let ptr = unsafe {
             Global.alloc(layout)
@@ -181,10 +184,17 @@ impl<T> Box<[T]> {
     /// ```
     #[unstable(feature = "new_uninit", issue = "63291")]
     pub fn new_uninit_slice(len: usize) -> Box<[mem::MaybeUninit<T>]> {
-        let layout = alloc::Layout::array::<mem::MaybeUninit<T>>(len).unwrap();
-        let ptr = unsafe { alloc::alloc(layout) };
-        let unique = Unique::new(ptr).unwrap_or_else(|| alloc::handle_alloc_error(layout));
-        let slice = unsafe { slice::from_raw_parts_mut(unique.cast().as_ptr(), len) };
+        let ptr = if mem::size_of::<T>() == 0 || len == 0 {
+            NonNull::dangling()
+        } else {
+            let layout = alloc::Layout::array::<mem::MaybeUninit<T>>(len).unwrap();
+            unsafe {
+                Global.alloc(layout)
+                    .unwrap_or_else(|_| alloc::handle_alloc_error(layout))
+                    .cast()
+            }
+        };
+        let slice = unsafe { slice::from_raw_parts_mut(ptr.as_ptr(), len) };
         Box(Unique::from(slice))
     }
 }
-- 
cgit 1.4.1-3-g733a5