From 63829a2a9f8cec9690da59541d68073a97994f35 Mon Sep 17 00:00:00 2001
From: "Sergey \"Shnatsel\" Davidoff" <sdavydov@google.com>
Date: Sat, 2 Nov 2019 18:33:17 +0100
Subject: [PATCH 1/4] Drop unnecessary `unsafe`

---
 src/macros.rs | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/src/macros.rs b/src/macros.rs
index 5662d289..19c7dcfa 100644
--- a/src/macros.rs
+++ b/src/macros.rs
@@ -470,19 +470,16 @@ macro_rules! crate_authors {
         impl Deref for CargoAuthors {
             type Target = str;
 
-            #[allow(unsafe_code)]
             fn deref(&self) -> &'static str {
                 static ONCE: Once = Once::new();
                 static mut VALUE: *const String = 0 as *const String;
 
-                unsafe {
-                    ONCE.call_once(|| {
-                        let s = env!("CARGO_PKG_AUTHORS").replace(':', $sep);
-                        VALUE = Box::into_raw(Box::new(s));
-                    });
+                ONCE.call_once(|| {
+                    let s = env!("CARGO_PKG_AUTHORS").replace(':', $sep);
+                    VALUE = Box::leak(s);
+                });
 
-                    &(*VALUE)[..]
-                }
+                &(*VALUE)[..]
             }
         }
 

From 0085bb7ee2f4ab7aac4797c2552adb1e004ced08 Mon Sep 17 00:00:00 2001
From: "Sergey \"Shnatsel\" Davidoff" <sdavydov@google.com>
Date: Sat, 2 Nov 2019 19:48:16 +0100
Subject: [PATCH 2/4] Make code actually work

---
 src/macros.rs | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/src/macros.rs b/src/macros.rs
index 19c7dcfa..95233475 100644
--- a/src/macros.rs
+++ b/src/macros.rs
@@ -459,7 +459,7 @@ macro_rules! crate_version {
 macro_rules! crate_authors {
     ($sep:expr) => {{
         use std::ops::Deref;
-        use std::sync::Once;
+        use std::boxed::Box;
 
         #[allow(missing_copy_implementations)]
         #[allow(dead_code)]
@@ -471,15 +471,9 @@ macro_rules! crate_authors {
             type Target = str;
 
             fn deref(&self) -> &'static str {
-                static ONCE: Once = Once::new();
-                static mut VALUE: *const String = 0 as *const String;
-
-                ONCE.call_once(|| {
-                    let s = env!("CARGO_PKG_AUTHORS").replace(':', $sep);
-                    VALUE = Box::leak(s);
-                });
-
-                &(*VALUE)[..]
+                let s: Box<String> = Box::new(env!("CARGO_PKG_AUTHORS").replace(':', $sep));
+                let s2 = Box::leak(s);
+                &*s2 // weird but compiler-suggested way to turn a String into &str
             }
         }
 

From 925956d594cac2cfcfc801179d537b1ad9ac99ca Mon Sep 17 00:00:00 2001
From: "Sergey \"Shnatsel\" Davidoff" <sdavydov@google.com>
Date: Sat, 2 Nov 2019 20:18:57 +0100
Subject: [PATCH 3/4] Do not leak a new string on every invocation of
 crate_authors!

---
 src/macros.rs | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/src/macros.rs b/src/macros.rs
index 95233475..d2446729 100644
--- a/src/macros.rs
+++ b/src/macros.rs
@@ -460,10 +460,12 @@ macro_rules! crate_authors {
     ($sep:expr) => {{
         use std::ops::Deref;
         use std::boxed::Box;
+        use std::cell::Cell;
 
         #[allow(missing_copy_implementations)]
         #[allow(dead_code)]
         struct CargoAuthors {
+            authors: Cell<Option<&'static str>>,
             __private_field: (),
         };
 
@@ -471,13 +473,22 @@ macro_rules! crate_authors {
             type Target = str;
 
             fn deref(&self) -> &'static str {
-                let s: Box<String> = Box::new(env!("CARGO_PKG_AUTHORS").replace(':', $sep));
-                let s2 = Box::leak(s);
-                &*s2 // weird but compiler-suggested way to turn a String into &str
+                let authors = self.authors.take();
+                if authors.is_some() {
+                    let unwrapped_authors = authors.unwrap();
+                    self.authors.replace(Some(unwrapped_authors));
+                    unwrapped_authors
+                } else {
+                    let s: Box<String> = Box::new(env!("CARGO_PKG_AUTHORS").replace(':', $sep));
+                    let static_string = Box::leak(s);
+                    self.authors.replace(Some(&*static_string));
+                    &*static_string // weird but compiler-suggested way to turn a String into &str
+                }
             }
         }
 
         &*CargoAuthors {
+            authors: std::cell::Cell::new(Option::None),
             __private_field: (),
         }
     }};

From 0a010a4371c8765996efd943b5240daab6fbf9c6 Mon Sep 17 00:00:00 2001
From: "Sergey \"Shnatsel\" Davidoff" <sdavydov@google.com>
Date: Sat, 2 Nov 2019 21:03:35 +0100
Subject: [PATCH 4/4] Add comment on performance

---
 src/macros.rs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/macros.rs b/src/macros.rs
index d2446729..03e518b0 100644
--- a/src/macros.rs
+++ b/src/macros.rs
@@ -479,6 +479,9 @@ macro_rules! crate_authors {
                     self.authors.replace(Some(unwrapped_authors));
                     unwrapped_authors
                 } else {
+                    // This caches the result for subsequent invocations of the same instance of the macro
+                    // to avoid performing one memory allocation per call.
+                    // If performance ever becomes a problem for this code, it should be moved to build.rs
                     let s: Box<String> = Box::new(env!("CARGO_PKG_AUTHORS").replace(':', $sep));
                     let static_string = Box::leak(s);
                     self.authors.replace(Some(&*static_string));