From 092bf2b50067a92e03da024b0406dca1c0e05d12 Mon Sep 17 00:00:00 2001
From: Austin Bonander <austin.bonander@gmail.com>
Date: Tue, 2 Oct 2018 03:42:01 -0700
Subject: [PATCH 1/2] make `CStr::from_bytes_with_nul_unchecked()` a const fn

closes #54678
---
 src/libstd/ffi/c_str.rs | 12 +++++++++++-
 src/libstd/lib.rs       |  1 +
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/libstd/ffi/c_str.rs b/src/libstd/ffi/c_str.rs
index 63dd12f782fda..dfec13cd2ec00 100644
--- a/src/libstd/ffi/c_str.rs
+++ b/src/libstd/ffi/c_str.rs
@@ -1040,7 +1040,8 @@ impl CStr {
     /// ```
     #[inline]
     #[stable(feature = "cstr_from_bytes", since = "1.10.0")]
-    pub unsafe fn from_bytes_with_nul_unchecked(bytes: &[u8]) -> &CStr {
+    #[rustc_const_unstable(feature = "const_cstr_unchecked")]
+    pub const unsafe fn from_bytes_with_nul_unchecked(bytes: &[u8]) -> &CStr {
         &*(bytes as *const [u8] as *const CStr)
     }
 
@@ -1471,4 +1472,13 @@ mod tests {
         assert_eq!(&*rc2, cstr);
         assert_eq!(&*arc2, cstr);
     }
+
+    #[test]
+    fn cstr_const_constructor() {
+        const CSTR: &'static CStr = unsafe {
+            CStr::from_bytes_with_nul_unchecked(b"Hello, world!\0")
+        };
+
+        assert_eq!(CSTR.to_str().unwrap(), "Hello, world!");
+    }
 }
diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
index 7ae4f2de4c36d..f8b1760975ae4 100644
--- a/src/libstd/lib.rs
+++ b/src/libstd/lib.rs
@@ -253,6 +253,7 @@
 #![feature(min_const_fn)]
 #![feature(const_int_ops)]
 #![feature(const_ip)]
+#![feature(const_raw_ptr_deref)]
 #![feature(core_intrinsics)]
 #![feature(dropck_eyepatch)]
 #![feature(exact_size_is_empty)]

From e0caaec6f92b7d9bf02278c6ed991cdb7139cd06 Mon Sep 17 00:00:00 2001
From: Austin Bonander <austin.bonander@gmail.com>
Date: Tue, 2 Oct 2018 04:26:16 -0700
Subject: [PATCH 2/2] make `CStr::from_bytes_with_nul_unchecked()` a const fn

closes #54678
---
 src/libstd/lib.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
index f8b1760975ae4..afe0b67e33020 100644
--- a/src/libstd/lib.rs
+++ b/src/libstd/lib.rs
@@ -254,6 +254,7 @@
 #![feature(const_int_ops)]
 #![feature(const_ip)]
 #![feature(const_raw_ptr_deref)]
+#![feature(const_cstr_unchecked)]
 #![feature(core_intrinsics)]
 #![feature(dropck_eyepatch)]
 #![feature(exact_size_is_empty)]