use Box::leak instead of forget

.github/workflows/lint_and_test.yml

@@ -4,32 +4,31 @@ name: Lint and Test
 on: [push, pull_request]
 
 jobs:
-  fmt:
-    name: fmt
+  lint:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v1
-      - run: rustup update
-      - run: rustup component add rustfmt
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          components: rustfmt,clippy
       - run: cargo fmt -- --check
+      - run: cargo clippy --all-targets
 
-  clippy:
-    name: clippy
+  test:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v1
-      - run: rustup update
-      - run: rustup component add clippy
-      - run: cargo clippy --all --all-targets --all-features
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+      - run: cargo build
+      - run: cargo test --verbose --all
+        env:
+          RUST_BACKTRACE: 1
 
-  test:
+  miri-test:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@nightly
         with:
-          submodules: true
-      - run: rustup update
-      - run: cargo build --all-features
-      - run: cargo test --verbose --all --all-features
-        env:
-          RUST_BACKTRACE: 1
+          components: miri
+      - run: cargo +nightly miri test

src/lib.rs

@@ -40,7 +40,7 @@ const OWN_FLAG: usize = !LEN_MASK;
 impl<'a> MownStr<'a> {
     pub const fn from_str(other: &'a str) -> MownStr<'a> {
         assert!(other.len() <= LEN_MASK);
-        // NB: The only 'const' constuctor for NonNull is new_unchecked
+        // NB: The only 'const' constructor for NonNull is new_unchecked
         // so we need an unsafe block.
 
         // SAFETY: we need a *mut u8 for new_unchecked,
@@ -140,17 +140,15 @@ impl<'a> From<&'a str> for MownStr<'a> {
 }
 
 impl<'a> From<Box<str>> for MownStr<'a> {
-    fn from(mut other: Box<str>) -> MownStr<'a> {
+    fn from(other: Box<str>) -> MownStr<'a> {
         let len = other.len();
         assert!(len <= LEN_MASK);
-        let addr = other.as_mut_ptr();
+        let addr = Box::leak(other).as_mut_ptr();
         let addr = unsafe {
             // SAFETY: ptr can not be null,
             NonNull::new_unchecked(addr)
         };
 
-        std::mem::forget(other);
-
         let xlen = len | OWN_FLAG;
         let _phd = PhantomData;
         MownStr { addr, xlen, _phd }
@@ -217,7 +215,7 @@ impl<'a> Eq for MownStr<'a> {}
 
 impl<'a> PartialOrd for MownStr<'a> {
     fn partial_cmp(&self, other: &MownStr<'a>) -> Option<std::cmp::Ordering> {
-        self.deref().partial_cmp(other.deref())
+        Some(self.cmp(other))
     }
 }
 
@@ -477,12 +475,16 @@ mod test {
     #[test]
     fn no_memory_leak() {
         // performs several MownStr allocation in sequence,
-        // droping each one before allocating the next one
+        // dropping each one before allocating the next one
         // (unless the v.pop() line below is commented out).
         //
         // If there is no memory leak,
         // the increase in memory should be roughly 1 time the allocated size;
         // otherwise, it should be roghly 10 times that size.
+        //
+        // NB: in miri, the value returned by get_rss_anon is fake,
+        // so no memory leak will ever be detected;
+        // but the test is still executed in miri to detect UB.
 
         let m0 = get_rss_anon();
         println!("memory = {} kB", m0);
@@ -515,6 +517,9 @@ mod test {
     const CAP: usize = 100_000_000;
 
     fn get_rss_anon() -> usize {
+        if cfg!(miri) {
+            return CAP; // return dummy value, as miri can not open files
+        }
         let txt = fs::read_to_string("/proc/self/status").expect("read proc status");
         let txt = txt.split("RssAnon:").nth(1).unwrap();
         let txt = txt.split(" kB").next().unwrap();