From 70c5af85e09be583128df5eda6b4de25a23387c1 Mon Sep 17 00:00:00 2001
From: Josh Stone <jistone@redhat.com>
Date: Wed, 13 Feb 2019 13:46:45 -0800
Subject: [PATCH 1/2] Avoid allocation in std::sys::unix::weak

If we add a terminating NUL to the name in the `weak!` macro, then
`fetch()` can use `CStr::from_bytes_with_nul()` instead of `CString`.
---
 src/libstd/sys/unix/weak.rs | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/libstd/sys/unix/weak.rs b/src/libstd/sys/unix/weak.rs
index d0242ca7422..9b80ad8d9b2 100644
--- a/src/libstd/sys/unix/weak.rs
+++ b/src/libstd/sys/unix/weak.rs
@@ -18,7 +18,7 @@
 
 use libc;
 
-use ffi::CString;
+use ffi::CStr;
 use marker;
 use mem;
 use sync::atomic::{AtomicUsize, Ordering};
@@ -26,7 +26,7 @@
 macro_rules! weak {
     (fn $name:ident($($t:ty),*) -> $ret:ty) => (
         static $name: ::sys::weak::Weak<unsafe extern fn($($t),*) -> $ret> =
-            ::sys::weak::Weak::new(stringify!($name));
+            ::sys::weak::Weak::new(concat!(stringify!($name), '\0'));
     )
 }
 
@@ -61,7 +61,7 @@ pub fn get(&self) -> Option<&F> {
 }
 
 unsafe fn fetch(name: &str) -> usize {
-    let name = match CString::new(name) {
+    let name = match CStr::from_bytes_with_nul(name.as_bytes()) {
         Ok(cstr) => cstr,
         Err(..) => return 0,
     };

From 33d80bfaa0f2a4ca996a942e6d65a932e72fec1b Mon Sep 17 00:00:00 2001
From: Josh Stone <jistone@redhat.com>
Date: Wed, 13 Feb 2019 14:07:08 -0800
Subject: [PATCH 2/2] Return without a reference in unix Weak::get()

---
 src/libstd/sys/unix/weak.rs | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/src/libstd/sys/unix/weak.rs b/src/libstd/sys/unix/weak.rs
index 9b80ad8d9b2..b60e241f10c 100644
--- a/src/libstd/sys/unix/weak.rs
+++ b/src/libstd/sys/unix/weak.rs
@@ -45,16 +45,15 @@ pub const fn new(name: &'static str) -> Weak<F> {
         }
     }
 
-    pub fn get(&self) -> Option<&F> {
+    pub fn get(&self) -> Option<F> {
         assert_eq!(mem::size_of::<F>(), mem::size_of::<usize>());
         unsafe {
             if self.addr.load(Ordering::SeqCst) == 1 {
                 self.addr.store(fetch(self.name), Ordering::SeqCst);
             }
-            if self.addr.load(Ordering::SeqCst) == 0 {
-                None
-            } else {
-                mem::transmute::<&AtomicUsize, Option<&F>>(&self.addr)
+            match self.addr.load(Ordering::SeqCst) {
+                0 => None,
+                addr => Some(mem::transmute_copy::<usize, F>(&addr)),
             }
         }
     }