use MaybeUninit

* instead of mem::uninitialized()
* There is still an unsafe {} required as maybe_uninit_slice is
  unstable.
* Once [MaybeUninit<T>; N]::maybe_uninit_slice() is stabilized, this can
  be used instead

Author: jordens

src/lib.rs

@@ -71,8 +71,3 @@ pub use self::ser::{to_string, to_vec};
 
 #[cfg(feature = "heapless")]
 pub use heapless;
-
-#[allow(deprecated)]
-unsafe fn uninitialized<T>() -> T {
-    core::mem::uninitialized()
-}

src/ser/mod.rs

@@ -1,5 +1,6 @@
 //! Serialize a Rust data structure into JSON data
 
+use core::mem::MaybeUninit;
 use core::{fmt, str};
 
 use serde::ser;
@@ -96,12 +97,12 @@ impl<'a> Serializer<'a> {
 // which take 200+ bytes of ROM / Flash
 macro_rules! serialize_unsigned {
     ($self:ident, $N:expr, $v:expr) => {{
-        let mut buf: [u8; $N] = unsafe { super::uninitialized() };
+        let mut buf: [MaybeUninit<u8>; $N] = [MaybeUninit::uninit(); $N];
 
         let mut v = $v;
         let mut i = $N - 1;
         loop {
-            buf[i] = (v % 10) as u8 + b'0';
+            buf[i].write((v % 10) as u8 + b'0');
             v /= 10;
 
             if v == 0 {
@@ -111,7 +112,10 @@ macro_rules! serialize_unsigned {
             }
         }
 
-        $self.extend_from_slice(&buf[i..])
+        // Note(feature): maybe_uninit_slice
+        let buf = unsafe { &*(&buf[i..] as *const _ as *const [u8]) };
+
+        $self.extend_from_slice(buf)
     }};
 }
 
@@ -126,10 +130,10 @@ macro_rules! serialize_signed {
             (false, v as $uxx)
         };
 
-        let mut buf: [u8; $N] = unsafe { super::uninitialized() };
+        let mut buf: [MaybeUninit<u8>; $N] = [MaybeUninit::uninit(); $N];
         let mut i = $N - 1;
         loop {
-            buf[i] = (v % 10) as u8 + b'0';
+            buf[i].write((v % 10) as u8 + b'0');
             v /= 10;
 
             i -= 1;
@@ -140,11 +144,15 @@ macro_rules! serialize_signed {
         }
 
         if signed {
-            buf[i] = b'-';
+            buf[i].write(b'-');
         } else {
             i += 1;
         }
-        $self.extend_from_slice(&buf[i..])
+
+        // Note(feature): maybe_uninit_slice
+        let buf = unsafe { &*(&buf[i..] as *const _ as *const [u8]) };
+
+        $self.extend_from_slice(buf)
     }};
 }