make basic allocation functions track_caller in Miri for nicer backtraces

Author: RalfJung

library/alloc/src/alloc.rs

@@ -89,6 +89,7 @@ pub use std::alloc::Global;
 #[stable(feature = "global_alloc", since = "1.28.0")]
 #[must_use = "losing the pointer will leak memory"]
 #[inline]
+#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
 pub unsafe fn alloc(layout: Layout) -> *mut u8 {
     unsafe {
         // Make sure we don't accidentally allow omitting the allocator shim in
@@ -113,6 +114,7 @@ pub unsafe fn alloc(layout: Layout) -> *mut u8 {
 /// See [`GlobalAlloc::dealloc`].
 #[stable(feature = "global_alloc", since = "1.28.0")]
 #[inline]
+#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
 pub unsafe fn dealloc(ptr: *mut u8, layout: Layout) {
     unsafe { __rust_dealloc(ptr, layout.size(), layout.align()) }
 }
@@ -132,6 +134,7 @@ pub unsafe fn dealloc(ptr: *mut u8, layout: Layout) {
 #[stable(feature = "global_alloc", since = "1.28.0")]
 #[must_use = "losing the pointer will leak memory"]
 #[inline]
+#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
 pub unsafe fn realloc(ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {
     unsafe { __rust_realloc(ptr, layout.size(), layout.align(), new_size) }
 }
@@ -166,13 +169,15 @@ pub unsafe fn realloc(ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8
 #[stable(feature = "global_alloc", since = "1.28.0")]
 #[must_use = "losing the pointer will leak memory"]
 #[inline]
+#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
 pub unsafe fn alloc_zeroed(layout: Layout) -> *mut u8 {
     unsafe { __rust_alloc_zeroed(layout.size(), layout.align()) }
 }
 
 #[cfg(not(test))]
 impl Global {
     #[inline]
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     fn alloc_impl(&self, layout: Layout, zeroed: bool) -> Result<NonNull<[u8]>, AllocError> {
         match layout.size() {
             0 => Ok(NonNull::slice_from_raw_parts(layout.dangling(), 0)),
@@ -187,6 +192,7 @@ impl Global {
 
     // SAFETY: Same as `Allocator::grow`
     #[inline]
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     unsafe fn grow_impl(
         &self,
         ptr: NonNull<u8>,
@@ -237,16 +243,19 @@ impl Global {
 #[cfg(not(test))]
 unsafe impl Allocator for Global {
     #[inline]
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
         self.alloc_impl(layout, false)
     }
 
     #[inline]
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     fn allocate_zeroed(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
         self.alloc_impl(layout, true)
     }
 
     #[inline]
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout) {
         if layout.size() != 0 {
             // SAFETY: `layout` is non-zero in size,
@@ -256,6 +265,7 @@ unsafe impl Allocator for Global {
     }
 
     #[inline]
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     unsafe fn grow(
         &self,
         ptr: NonNull<u8>,
@@ -267,6 +277,7 @@ unsafe impl Allocator for Global {
     }
 
     #[inline]
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     unsafe fn grow_zeroed(
         &self,
         ptr: NonNull<u8>,
@@ -278,6 +289,7 @@ unsafe impl Allocator for Global {
     }
 
     #[inline]
+    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     unsafe fn shrink(
         &self,
         ptr: NonNull<u8>,
@@ -325,6 +337,7 @@ unsafe impl Allocator for Global {
 #[cfg(all(not(no_global_oom_handling), not(test)))]
 #[lang = "exchange_malloc"]
 #[inline]
+#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
 unsafe fn exchange_malloc(size: usize, align: usize) -> *mut u8 {
     let layout = unsafe { Layout::from_size_align_unchecked(size, align) };
     match Global.allocate(layout) {

library/core/src/mem/mod.rs

@@ -859,6 +859,7 @@ pub fn take<T: Default>(dest: &mut T) -> T {
 #[must_use = "if you don't need the old value, you can just assign the new value directly"]
 #[rustc_const_unstable(feature = "const_replace", issue = "83164")]
 #[cfg_attr(not(test), rustc_diagnostic_item = "mem_replace")]
+#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
 pub const fn replace<T>(dest: &mut T, src: T) -> T {
     // It may be tempting to use `swap` to avoid `unsafe` here. Don't!
     // The compiler optimizes the implementation below to two `memcpy`s

src/tools/miri/tests/fail/alloc/deallocate-bad-alignment.rs

@@ -1,10 +1,8 @@
 use std::alloc::{alloc, dealloc, Layout};
 
-//@error-in-other-file: has size 1 and alignment 1, but gave size 1 and alignment 2
-
 fn main() {
     unsafe {
         let x = alloc(Layout::from_size_align_unchecked(1, 1));
-        dealloc(x, Layout::from_size_align_unchecked(1, 2));
+        dealloc(x, Layout::from_size_align_unchecked(1, 2)); //~ERROR: has size 1 and alignment 1, but gave size 1 and alignment 2
     }
 }

src/tools/miri/tests/fail/alloc/deallocate-bad-alignment.stderr

@@ -1,18 +1,13 @@
 error: Undefined Behavior: incorrect layout on deallocation: ALLOC has size 1 and alignment ALIGN, but gave size 1 and alignment ALIGN
-  --> RUSTLIB/alloc/src/alloc.rs:LL:CC
+  --> $DIR/deallocate-bad-alignment.rs:LL:CC
    |
-LL |     unsafe { __rust_dealloc(ptr, layout.size(), layout.align()) }
-   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ incorrect layout on deallocation: ALLOC has size 1 and alignment ALIGN, but gave size 1 and alignment ALIGN
+LL |         dealloc(x, Layout::from_size_align_unchecked(1, 2));
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ incorrect layout on deallocation: ALLOC has size 1 and alignment ALIGN, but gave size 1 and alignment ALIGN
    |
    = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
    = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
    = note: BACKTRACE:
-   = note: inside `std::alloc::dealloc` at RUSTLIB/alloc/src/alloc.rs:LL:CC
-note: inside `main`
-  --> $DIR/deallocate-bad-alignment.rs:LL:CC
-   |
-LL |         dealloc(x, Layout::from_size_align_unchecked(1, 2));
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: inside `main` at $DIR/deallocate-bad-alignment.rs:LL:CC
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 

src/tools/miri/tests/fail/alloc/deallocate-bad-size.rs

@@ -1,10 +1,8 @@
 use std::alloc::{alloc, dealloc, Layout};
 
-//@error-in-other-file: has size 1 and alignment 1, but gave size 2 and alignment 1
-
 fn main() {
     unsafe {
         let x = alloc(Layout::from_size_align_unchecked(1, 1));
-        dealloc(x, Layout::from_size_align_unchecked(2, 1));
+        dealloc(x, Layout::from_size_align_unchecked(2, 1)); //~ERROR: has size 1 and alignment 1, but gave size 2 and alignment 1
     }
 }

src/tools/miri/tests/fail/alloc/deallocate-bad-size.stderr

@@ -1,18 +1,13 @@
 error: Undefined Behavior: incorrect layout on deallocation: ALLOC has size 1 and alignment ALIGN, but gave size 2 and alignment ALIGN
-  --> RUSTLIB/alloc/src/alloc.rs:LL:CC
+  --> $DIR/deallocate-bad-size.rs:LL:CC
    |
-LL |     unsafe { __rust_dealloc(ptr, layout.size(), layout.align()) }
-   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ incorrect layout on deallocation: ALLOC has size 1 and alignment ALIGN, but gave size 2 and alignment ALIGN
+LL |         dealloc(x, Layout::from_size_align_unchecked(2, 1));
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ incorrect layout on deallocation: ALLOC has size 1 and alignment ALIGN, but gave size 2 and alignment ALIGN
    |
    = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
    = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
    = note: BACKTRACE:
-   = note: inside `std::alloc::dealloc` at RUSTLIB/alloc/src/alloc.rs:LL:CC
-note: inside `main`
-  --> $DIR/deallocate-bad-size.rs:LL:CC
-   |
-LL |         dealloc(x, Layout::from_size_align_unchecked(2, 1));
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: inside `main` at $DIR/deallocate-bad-size.rs:LL:CC
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 

src/tools/miri/tests/fail/alloc/deallocate-twice.rs

@@ -1,11 +1,9 @@
 use std::alloc::{alloc, dealloc, Layout};
 
-//@error-in-other-file: has been freed
-
 fn main() {
     unsafe {
         let x = alloc(Layout::from_size_align_unchecked(1, 1));
         dealloc(x, Layout::from_size_align_unchecked(1, 1));
-        dealloc(x, Layout::from_size_align_unchecked(1, 1));
+        dealloc(x, Layout::from_size_align_unchecked(1, 1)); //~ERROR: has been freed
     }
 }

src/tools/miri/tests/fail/alloc/deallocate-twice.stderr

@@ -1,8 +1,8 @@
 error: Undefined Behavior: memory access failed: ALLOC has been freed, so this pointer is dangling
-  --> RUSTLIB/alloc/src/alloc.rs:LL:CC
+  --> $DIR/deallocate-twice.rs:LL:CC
    |
-LL |     unsafe { __rust_dealloc(ptr, layout.size(), layout.align()) }
-   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ memory access failed: ALLOC has been freed, so this pointer is dangling
+LL |         dealloc(x, Layout::from_size_align_unchecked(1, 1));
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ memory access failed: ALLOC has been freed, so this pointer is dangling
    |
    = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
    = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
@@ -17,12 +17,7 @@ help: ALLOC was deallocated here:
 LL |         dealloc(x, Layout::from_size_align_unchecked(1, 1));
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: BACKTRACE (of the first span):
-   = note: inside `std::alloc::dealloc` at RUSTLIB/alloc/src/alloc.rs:LL:CC
-note: inside `main`
-  --> $DIR/deallocate-twice.rs:LL:CC
-   |
-LL |         dealloc(x, Layout::from_size_align_unchecked(1, 1));
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: inside `main` at $DIR/deallocate-twice.rs:LL:CC
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 

src/tools/miri/tests/fail/alloc/reallocate-bad-size.rs

@@ -1,10 +1,8 @@
 use std::alloc::{alloc, realloc, Layout};
 
-//@error-in-other-file: has size 1 and alignment 1, but gave size 2 and alignment 1
-
 fn main() {
     unsafe {
         let x = alloc(Layout::from_size_align_unchecked(1, 1));
-        let _y = realloc(x, Layout::from_size_align_unchecked(2, 1), 1);
+        let _y = realloc(x, Layout::from_size_align_unchecked(2, 1), 1); //~ERROR: has size 1 and alignment 1, but gave size 2 and alignment 1
     }
 }

src/tools/miri/tests/fail/alloc/reallocate-bad-size.stderr

@@ -1,18 +1,13 @@
 error: Undefined Behavior: incorrect layout on deallocation: ALLOC has size 1 and alignment ALIGN, but gave size 2 and alignment ALIGN
-  --> RUSTLIB/alloc/src/alloc.rs:LL:CC
+  --> $DIR/reallocate-bad-size.rs:LL:CC
    |
-LL |     unsafe { __rust_realloc(ptr, layout.size(), layout.align(), new_size) }
-   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ incorrect layout on deallocation: ALLOC has size 1 and alignment ALIGN, but gave size 2 and alignment ALIGN
+LL |         let _y = realloc(x, Layout::from_size_align_unchecked(2, 1), 1);
+   |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ incorrect layout on deallocation: ALLOC has size 1 and alignment ALIGN, but gave size 2 and alignment ALIGN
    |
    = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
    = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
    = note: BACKTRACE:
-   = note: inside `std::alloc::realloc` at RUSTLIB/alloc/src/alloc.rs:LL:CC
-note: inside `main`
-  --> $DIR/reallocate-bad-size.rs:LL:CC
-   |
-LL |         let _y = realloc(x, Layout::from_size_align_unchecked(2, 1), 1);
-   |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: inside `main` at $DIR/reallocate-bad-size.rs:LL:CC
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 

src/tools/miri/tests/fail/alloc/reallocate-dangling.rs

@@ -1,11 +1,9 @@
 use std::alloc::{alloc, dealloc, realloc, Layout};
 
-//@error-in-other-file: has been freed
-
 fn main() {
     unsafe {
         let x = alloc(Layout::from_size_align_unchecked(1, 1));
         dealloc(x, Layout::from_size_align_unchecked(1, 1));
-        let _z = realloc(x, Layout::from_size_align_unchecked(1, 1), 1);
+        let _z = realloc(x, Layout::from_size_align_unchecked(1, 1), 1); //~ERROR: has been freed
     }
 }

src/tools/miri/tests/fail/alloc/reallocate-dangling.stderr

@@ -1,8 +1,8 @@
 error: Undefined Behavior: memory access failed: ALLOC has been freed, so this pointer is dangling
-  --> RUSTLIB/alloc/src/alloc.rs:LL:CC
+  --> $DIR/reallocate-dangling.rs:LL:CC
    |
-LL |     unsafe { __rust_realloc(ptr, layout.size(), layout.align(), new_size) }
-   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ memory access failed: ALLOC has been freed, so this pointer is dangling
+LL |         let _z = realloc(x, Layout::from_size_align_unchecked(1, 1), 1);
+   |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ memory access failed: ALLOC has been freed, so this pointer is dangling
    |
    = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
    = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
@@ -17,12 +17,7 @@ help: ALLOC was deallocated here:
 LL |         dealloc(x, Layout::from_size_align_unchecked(1, 1));
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: BACKTRACE (of the first span):
-   = note: inside `std::alloc::realloc` at RUSTLIB/alloc/src/alloc.rs:LL:CC
-note: inside `main`
-  --> $DIR/reallocate-dangling.rs:LL:CC
-   |
-LL |         let _z = realloc(x, Layout::from_size_align_unchecked(1, 1), 1);
-   |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: inside `main` at $DIR/reallocate-dangling.rs:LL:CC
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 

src/tools/miri/tests/fail/alloc/stack_free.stderr

@@ -1,14 +1,12 @@
 error: Undefined Behavior: deallocating ALLOC, which is stack variable memory, using Rust heap deallocation operation
-  --> RUSTLIB/alloc/src/alloc.rs:LL:CC
+  --> RUSTLIB/alloc/src/boxed.rs:LL:CC
    |
-LL |     unsafe { __rust_dealloc(ptr, layout.size(), layout.align()) }
-   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ deallocating ALLOC, which is stack variable memory, using Rust heap deallocation operation
+LL |                 self.1.deallocate(From::from(ptr.cast()), layout);
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ deallocating ALLOC, which is stack variable memory, using Rust heap deallocation operation
    |
    = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
    = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
    = note: BACKTRACE:
-   = note: inside `std::alloc::dealloc` at RUSTLIB/alloc/src/alloc.rs:LL:CC
-   = note: inside `<std::alloc::Global as std::alloc::Allocator>::deallocate` at RUSTLIB/alloc/src/alloc.rs:LL:CC
    = note: inside `<std::boxed::Box<i32> as std::ops::Drop>::drop` at RUSTLIB/alloc/src/boxed.rs:LL:CC
    = note: inside `std::ptr::drop_in_place::<std::boxed::Box<i32>> - shim(Some(std::boxed::Box<i32>))` at RUSTLIB/core/src/ptr/mod.rs:LL:CC
    = note: inside `std::mem::drop::<std::boxed::Box<i32>>` at RUSTLIB/core/src/mem/mod.rs:LL:CC

src/tools/miri/tests/fail/both_borrows/aliasing_mut4.tree.stderr

@@ -1,8 +1,8 @@
 error: Undefined Behavior: write access through <TAG> at ALLOC[0x0] is forbidden
-  --> RUSTLIB/core/src/mem/mod.rs:LL:CC
+  --> RUSTLIB/core/src/cell.rs:LL:CC
    |
-LL |         ptr::write(dest, src);
-   |         ^^^^^^^^^^^^^^^^^^^^^ write access through <TAG> at ALLOC[0x0] is forbidden
+LL |         mem::replace(unsafe { &mut *self.value.get() }, val)
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ write access through <TAG> at ALLOC[0x0] is forbidden
    |
    = help: this indicates a potential bug in the program: it performed an invalid operation, but the Tree Borrows rules it violated are still experimental
    = help: the accessed tag <TAG> is foreign to the protected tag <TAG> (i.e., it is not a child)
@@ -19,7 +19,6 @@ help: the protected tag <TAG> was created here, in the initial state Frozen
 LL | pub fn safe(x: &i32, y: &mut Cell<i32>) {
    |             ^
    = note: BACKTRACE (of the first span):
-   = note: inside `std::mem::replace::<i32>` at RUSTLIB/core/src/mem/mod.rs:LL:CC
    = note: inside `std::cell::Cell::<i32>::replace` at RUSTLIB/core/src/cell.rs:LL:CC
    = note: inside `std::cell::Cell::<i32>::set` at RUSTLIB/core/src/cell.rs:LL:CC
 note: inside `safe`

src/tools/miri/tests/fail/both_borrows/newtype_pair_retagging.tree.stderr

@@ -1,8 +1,8 @@
 error: Undefined Behavior: deallocation through <TAG> at ALLOC[0x0] is forbidden
-  --> RUSTLIB/alloc/src/alloc.rs:LL:CC
+  --> RUSTLIB/alloc/src/boxed.rs:LL:CC
    |
-LL |     unsafe { __rust_dealloc(ptr, layout.size(), layout.align()) }
-   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ deallocation through <TAG> at ALLOC[0x0] is forbidden
+LL |                 self.1.deallocate(From::from(ptr.cast()), layout);
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ deallocation through <TAG> at ALLOC[0x0] is forbidden
    |
    = help: this indicates a potential bug in the program: it performed an invalid operation, but the Tree Borrows rules it violated are still experimental
    = help: the accessed tag <TAG> is foreign to the protected tag <TAG> (i.e., it is not a child)
@@ -25,8 +25,6 @@ LL |             || drop(Box::from_raw(ptr)),
    |                     ^^^^^^^^^^^^^^^^^^
    = help: this transition corresponds to a temporary loss of write permissions until function exit
    = note: BACKTRACE (of the first span):
-   = note: inside `std::alloc::dealloc` at RUSTLIB/alloc/src/alloc.rs:LL:CC
-   = note: inside `<std::alloc::Global as std::alloc::Allocator>::deallocate` at RUSTLIB/alloc/src/alloc.rs:LL:CC
    = note: inside `<std::boxed::Box<i32> as std::ops::Drop>::drop` at RUSTLIB/alloc/src/boxed.rs:LL:CC
    = note: inside `std::ptr::drop_in_place::<std::boxed::Box<i32>> - shim(Some(std::boxed::Box<i32>))` at RUSTLIB/core/src/ptr/mod.rs:LL:CC
    = note: inside `std::mem::drop::<std::boxed::Box<i32>>` at RUSTLIB/core/src/mem/mod.rs:LL:CC