diff options
| -rw-r--r-- | compiler/rustc_mir/src/transform/check_const_item_mutation.rs | 14 | ||||
| -rw-r--r-- | src/test/ui/lint/lint-const-item-mutation.rs | 13 | ||||
| -rw-r--r-- | src/test/ui/lint/lint-const-item-mutation.stderr | 46 |
3 files changed, 44 insertions, 29 deletions
diff --git a/compiler/rustc_mir/src/transform/check_const_item_mutation.rs b/compiler/rustc_mir/src/transform/check_const_item_mutation.rs index 70c1aed0957..0281c478a6c 100644 --- a/compiler/rustc_mir/src/transform/check_const_item_mutation.rs +++ b/compiler/rustc_mir/src/transform/check_const_item_mutation.rs @@ -60,11 +60,15 @@ impl<'a, 'tcx> Visitor<'tcx> for ConstMutationChecker<'a, 'tcx> { // so emitting a lint would be redundant. if !lhs.projection.is_empty() { if let Some(def_id) = self.is_const_item(lhs.local) { - self.lint_const_item_usage(def_id, loc, |lint| { - let mut lint = lint.build("attempting to modify a `const` item"); - lint.note("each usage of a `const` item creates a new temporary - the original `const` item will not be modified"); - lint - }) + // Don't lint on writes through a pointer + // (e.g. `unsafe { *FOO = 0; *BAR.field = 1; }`) + if !matches!(lhs.projection.last(), Some(PlaceElem::Deref)) { + self.lint_const_item_usage(def_id, loc, |lint| { + let mut lint = lint.build("attempting to modify a `const` item"); + lint.note("each usage of a `const` item creates a new temporary - the original `const` item will not be modified"); + lint + }) + } } } // We are looking for MIR of the form: diff --git a/src/test/ui/lint/lint-const-item-mutation.rs b/src/test/ui/lint/lint-const-item-mutation.rs index 92d29a7dae4..43371560e02 100644 --- a/src/test/ui/lint/lint-const-item-mutation.rs +++ b/src/test/ui/lint/lint-const-item-mutation.rs @@ -3,13 +3,15 @@ struct MyStruct { field: bool, inner_array: [char; 1], + raw_ptr: *mut u8 } impl MyStruct { fn use_mut(&mut self) {} } const ARRAY: [u8; 1] = [25]; -const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'] }; +const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'], raw_ptr: 2 as *mut u8 }; +const RAW_PTR: *mut u8 = 1 as *mut u8; fn main() { ARRAY[0] = 5; //~ WARN attempting to modify @@ -18,4 +20,13 @@ fn main() { MY_STRUCT.use_mut(); //~ WARN taking &mut MY_STRUCT; //~ WARN taking (&mut MY_STRUCT).use_mut(); //~ WARN taking + + // Test that we don't warn when writing through + // a raw pointer + // This is U.B., but this test is check-pass, + // so this never actually executes + unsafe { + *RAW_PTR = 0; + *MY_STRUCT.raw_ptr = 0; + } } diff --git a/src/test/ui/lint/lint-const-item-mutation.stderr b/src/test/ui/lint/lint-const-item-mutation.stderr index 2d8f2c49744..c5a221128ff 100644 --- a/src/test/ui/lint/lint-const-item-mutation.stderr +++ b/src/test/ui/lint/lint-const-item-mutation.stderr @@ -1,5 +1,5 @@ warning: attempting to modify a `const` item - --> $DIR/lint-const-item-mutation.rs:15:5 + --> $DIR/lint-const-item-mutation.rs:17:5 | LL | ARRAY[0] = 5; | ^^^^^^^^^^^^ @@ -7,39 +7,39 @@ LL | ARRAY[0] = 5; = note: `#[warn(const_item_mutation)]` on by default = note: each usage of a `const` item creates a new temporary - the original `const` item will not be modified note: `const` item defined here - --> $DIR/lint-const-item-mutation.rs:11:1 + --> $DIR/lint-const-item-mutation.rs:12:1 | LL | const ARRAY: [u8; 1] = [25]; | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ warning: attempting to modify a `const` item - --> $DIR/lint-const-item-mutation.rs:16:5 + --> $DIR/lint-const-item-mutation.rs:18:5 | LL | MY_STRUCT.field = false; | ^^^^^^^^^^^^^^^^^^^^^^^ | = note: each usage of a `const` item creates a new temporary - the original `const` item will not be modified note: `const` item defined here - --> $DIR/lint-const-item-mutation.rs:12:1 + --> $DIR/lint-const-item-mutation.rs:13:1 | -LL | const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'] }; - | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +LL | const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'], raw_ptr: 2 as *mut u8 }; + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ warning: attempting to modify a `const` item - --> $DIR/lint-const-item-mutation.rs:17:5 + --> $DIR/lint-const-item-mutation.rs:19:5 | LL | MY_STRUCT.inner_array[0] = 'b'; | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | = note: each usage of a `const` item creates a new temporary - the original `const` item will not be modified note: `const` item defined here - --> $DIR/lint-const-item-mutation.rs:12:1 + --> $DIR/lint-const-item-mutation.rs:13:1 | -LL | const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'] }; - | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +LL | const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'], raw_ptr: 2 as *mut u8 }; + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ warning: taking a mutable reference to a `const` item - --> $DIR/lint-const-item-mutation.rs:18:5 + --> $DIR/lint-const-item-mutation.rs:20:5 | LL | MY_STRUCT.use_mut(); | ^^^^^^^^^^^^^^^^^^^ @@ -47,18 +47,18 @@ LL | MY_STRUCT.use_mut(); = note: each usage of a `const` item creates a new temporary = note: the mutable reference will refer to this temporary, not the original `const` item note: mutable reference created due to call to this method - --> $DIR/lint-const-item-mutation.rs:8:5 + --> $DIR/lint-const-item-mutation.rs:9:5 | LL | fn use_mut(&mut self) {} | ^^^^^^^^^^^^^^^^^^^^^ note: `const` item defined here - --> $DIR/lint-const-item-mutation.rs:12:1 + --> $DIR/lint-const-item-mutation.rs:13:1 | -LL | const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'] }; - | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +LL | const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'], raw_ptr: 2 as *mut u8 }; + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ warning: taking a mutable reference to a `const` item - --> $DIR/lint-const-item-mutation.rs:19:5 + --> $DIR/lint-const-item-mutation.rs:21:5 | LL | &mut MY_STRUCT; | ^^^^^^^^^^^^^^ @@ -66,13 +66,13 @@ LL | &mut MY_STRUCT; = note: each usage of a `const` item creates a new temporary = note: the mutable reference will refer to this temporary, not the original `const` item note: `const` item defined here - --> $DIR/lint-const-item-mutation.rs:12:1 + --> $DIR/lint-const-item-mutation.rs:13:1 | -LL | const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'] }; - | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +LL | const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'], raw_ptr: 2 as *mut u8 }; + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ warning: taking a mutable reference to a `const` item - --> $DIR/lint-const-item-mutation.rs:20:5 + --> $DIR/lint-const-item-mutation.rs:22:5 | LL | (&mut MY_STRUCT).use_mut(); | ^^^^^^^^^^^^^^^^ @@ -80,10 +80,10 @@ LL | (&mut MY_STRUCT).use_mut(); = note: each usage of a `const` item creates a new temporary = note: the mutable reference will refer to this temporary, not the original `const` item note: `const` item defined here - --> $DIR/lint-const-item-mutation.rs:12:1 + --> $DIR/lint-const-item-mutation.rs:13:1 | -LL | const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'] }; - | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +LL | const MY_STRUCT: MyStruct = MyStruct { field: true, inner_array: ['a'], raw_ptr: 2 as *mut u8 }; + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ warning: 6 warnings emitted |