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Evaluate place expression in PlaceMention.

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This commit is contained in:
Camille GILLOT 2022-11-24 19:09:27 +00:00
parent 409661936f
commit ddfa2463e2
13 changed files with 159 additions and 19 deletions
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8
compiler/rustc_borrowck/src/def_use.rs
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@ -52,12 +52,16 @@ pub fn categorize(context: PlaceContext) -> Option<DefUse> {
PlaceContext::NonMutatingUse(NonMutatingUseContext::ShallowBorrow) |
PlaceContext::NonMutatingUse(NonMutatingUseContext::UniqueBorrow) |
// `PlaceMention` and `AscribeUserType` both evaluate the place, which must not
// contain dangling references.
PlaceContext::NonUse(NonUseContext::PlaceMention) |
PlaceContext::NonUse(NonUseContext::AscribeUserTy) |
PlaceContext::MutatingUse(MutatingUseContext::AddressOf) |
PlaceContext::NonMutatingUse(NonMutatingUseContext::AddressOf) |
PlaceContext::NonMutatingUse(NonMutatingUseContext::Inspect) |
PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy) |
PlaceContext::NonMutatingUse(NonMutatingUseContext::Move) |
PlaceContext::NonUse(NonUseContext::AscribeUserTy) |
PlaceContext::MutatingUse(MutatingUseContext::Retag) =>
Some(DefUse::Use),
@ -72,8 +76,6 @@ pub fn categorize(context: PlaceContext) -> Option<DefUse> {
PlaceContext::MutatingUse(MutatingUseContext::Drop) =>
Some(DefUse::Drop),
// This statement exists to help unsafeck. It does not require the place to be live.
PlaceContext::NonUse(NonUseContext::PlaceMention) => None,
// Debug info is neither def nor use.
PlaceContext::NonUse(NonUseContext::VarDebugInfo) => None,

2
compiler/rustc_borrowck/src/invalidation.rs
View File

@ -79,7 +79,7 @@ fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) {
}
// Only relevant for mir typeck
StatementKind::AscribeUserType(..)
// Only relevant for unsafeck
// Only relevant for liveness and unsafeck
| StatementKind::PlaceMention(..)
// Doesn't have any language semantics
| StatementKind::Coverage(..)

2
compiler/rustc_borrowck/src/lib.rs
View File

@ -665,7 +665,7 @@ fn visit_statement_before_primary_effect(
}
// Only relevant for mir typeck
StatementKind::AscribeUserType(..)
// Only relevant for unsafeck
// Only relevant for liveness and unsafeck
| StatementKind::PlaceMention(..)
// Doesn't have any language semantics
| StatementKind::Coverage(..)

10
compiler/rustc_const_eval/src/interpret/step.rs
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@ -113,8 +113,14 @@ pub fn statement(&mut self, stmt: &mir::Statement<'tcx>) -> InterpResult<'tcx> {
Intrinsic(box intrinsic) => self.emulate_nondiverging_intrinsic(intrinsic)?,
// Statements we do not track.
PlaceMention(..) | AscribeUserType(..) => {}
// Evaluate the place expression, without reading from it.
PlaceMention(box place) => {
let _ = self.eval_place(*place)?;
}
// This exists purely to guide borrowck lifetime inference, and does not have
// an operational effect.
AscribeUserType(..) => {}
// Currently, Miri discards Coverage statements. Coverage statements are only injected
// via an optional compile time MIR pass and have no side effects. Since Coverage

3
compiler/rustc_middle/src/mir/syntax.rs
View File

@ -331,7 +331,8 @@ pub enum StatementKind<'tcx> {
/// This is especially useful for `let _ = PLACE;` bindings that desugar to a single
/// `PlaceMention(PLACE)`.
///
/// When executed at runtime this is a nop.
/// When executed at runtime, this computes the given place, but then discards
/// it without doing a load. It is UB if the place is not pointing to live memory.
///
/// Disallowed after drop elaboration.
PlaceMention(Box<Place<'tcx>>),

4
src/tools/clippy/tests/ui/option_if_let_else.fixed
View File

@ -25,7 +25,7 @@ fn else_if_option(string: Option<&str>) -> Option<(bool, &str)> {
fn unop_bad(string: &Option<&str>, mut num: Option<i32>) {
let _ = string.map_or(0, |s| s.len());
let _ = num.as_ref().map_or(&0, |s| s);
let _ = num.as_mut().map_or(&mut 0, |s| {
let _ = num.as_mut().map_or(&0, |s| {
*s += 1;
s
});
@ -34,7 +34,7 @@ fn unop_bad(string: &Option<&str>, mut num: Option<i32>) {
s += 1;
s
});
let _ = num.as_mut().map_or(&mut 0, |s| {
let _ = num.as_mut().map_or(&0, |s| {
*s += 1;
s
});

4
src/tools/clippy/tests/ui/option_if_let_else.rs
View File

@ -33,7 +33,7 @@ fn unop_bad(string: &Option<&str>, mut num: Option<i32>) {
*s += 1;
s
} else {
&mut 0
&0
};
let _ = if let Some(ref s) = num { s } else { &0 };
let _ = if let Some(mut s) = num {
@ -46,7 +46,7 @@ fn unop_bad(string: &Option<&str>, mut num: Option<i32>) {
*s += 1;
s
} else {
&mut 0
&0
};
}

8
src/tools/clippy/tests/ui/option_if_let_else.stderr
View File

@ -30,13 +30,13 @@ LL | let _ = if let Some(s) = &mut num {
LL | | *s += 1;
LL | | s
LL | | } else {
LL | | &mut 0
LL | | &0
LL | | };
| |_____^
|
help: try
|
LL ~ let _ = num.as_mut().map_or(&mut 0, |s| {
LL ~ let _ = num.as_mut().map_or(&0, |s| {
LL + *s += 1;
LL + s
LL ~ });
@ -76,13 +76,13 @@ LL | let _ = if let Some(ref mut s) = num {
LL | | *s += 1;
LL | | s
LL | | } else {
LL | | &mut 0
LL | | &0
LL | | };
| |_____^
|
help: try
|
LL ~ let _ = num.as_mut().map_or(&mut 0, |s| {
LL ~ let _ = num.as_mut().map_or(&0, |s| {
LL + *s += 1;
LL + s
LL ~ });

11
src/tools/miri/tests/fail/dangling_pointers/dangling_pointer_deref_underscore.rs Normal file
View File

@ -0,0 +1,11 @@
// Make sure we find these even with many checks disabled.
//@compile-flags: -Zmiri-disable-alignment-check -Zmiri-disable-stacked-borrows -Zmiri-disable-validation
fn main() {
let p = {
let b = Box::new(42);
&*b as *const i32
};
let _ = unsafe { *p }; //~ ERROR: dereferenced after this allocation got freed
panic!("this should never print");
}

15
src/tools/miri/tests/fail/dangling_pointers/dangling_pointer_deref_underscore.stderr Normal file
View File

@ -0,0 +1,15 @@
error: Undefined Behavior: pointer to ALLOC was dereferenced after this allocation got freed
--> $DIR/dangling_pointer_deref_underscore.rs:LL:CC
|
LL | let _ = unsafe { *p };
| ^^ pointer to ALLOC was dereferenced after this allocation got freed
|
= 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 `main` at $DIR/dangling_pointer_deref_underscore.rs:LL:CC
note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
error: aborting due to previous error

30
tests/ui/borrowck/let_underscore_temporary.rs
View File

@ -1,4 +1,4 @@
// check-pass
// check-fail
fn let_underscore(string: &Option<&str>, mut num: Option<i32>) {
let _ = if let Some(s) = *string { s.len() } else { 0 };
@ -8,6 +8,7 @@ fn let_underscore(string: &Option<&str>, mut num: Option<i32>) {
s
} else {
&mut 0
//~^ ERROR temporary value dropped while borrowed
};
let _ = if let Some(ref s) = num { s } else { &0 };
let _ = if let Some(mut s) = num {
@ -21,6 +22,33 @@ fn let_underscore(string: &Option<&str>, mut num: Option<i32>) {
s
} else {
&mut 0
//~^ ERROR temporary value dropped while borrowed
};
}
fn let_ascribe(string: &Option<&str>, mut num: Option<i32>) {
let _: _ = if let Some(s) = *string { s.len() } else { 0 };
let _: _ = if let Some(s) = &num { s } else { &0 };
let _: _ = if let Some(s) = &mut num {
*s += 1;
s
} else {
&mut 0
//~^ ERROR temporary value dropped while borrowed
};
let _: _ = if let Some(ref s) = num { s } else { &0 };
let _: _ = if let Some(mut s) = num {
s += 1;
s
} else {
0
};
let _: _ = if let Some(ref mut s) = num {
*s += 1;
s
} else {
&mut 0
//~^ ERROR temporary value dropped while borrowed
};
}

79
tests/ui/borrowck/let_underscore_temporary.stderr Normal file
View File

@ -0,0 +1,79 @@
error[E0716]: temporary value dropped while borrowed
--> $DIR/let_underscore_temporary.rs:10:14
|
LL | let _ = if let Some(s) = &mut num {
| _____________-
LL | | *s += 1;
LL | | s
LL | | } else {
LL | | &mut 0
| | ^ creates a temporary value which is freed while still in use
LL | |
LL | | };
| | -
| | |
| |_____temporary value is freed at the end of this statement
| borrow later used here
|
= note: consider using a `let` binding to create a longer lived value
error[E0716]: temporary value dropped while borrowed
--> $DIR/let_underscore_temporary.rs:24:14
|
LL | let _ = if let Some(ref mut s) = num {
| _____________-
LL | | *s += 1;
LL | | s
LL | | } else {
LL | | &mut 0
| | ^ creates a temporary value which is freed while still in use
LL | |
LL | | };
| | -
| | |
| |_____temporary value is freed at the end of this statement
| borrow later used here
|
= note: consider using a `let` binding to create a longer lived value
error[E0716]: temporary value dropped while borrowed
--> $DIR/let_underscore_temporary.rs:36:14
|
LL | let _: _ = if let Some(s) = &mut num {
| ________________-
LL | | *s += 1;
LL | | s
LL | | } else {
LL | | &mut 0
| | ^ creates a temporary value which is freed while still in use
LL | |
LL | | };
| | -
| | |
| |_____temporary value is freed at the end of this statement
| borrow later used here
|
= note: consider using a `let` binding to create a longer lived value
error[E0716]: temporary value dropped while borrowed
--> $DIR/let_underscore_temporary.rs:50:14
|
LL | let _: _ = if let Some(ref mut s) = num {
| ________________-
LL | | *s += 1;
LL | | s
LL | | } else {
LL | | &mut 0
| | ^ creates a temporary value which is freed while still in use
LL | |
LL | | };
| | -
| | |
| |_____temporary value is freed at the end of this statement
| borrow later used here
|
= note: consider using a `let` binding to create a longer lived value
error: aborting due to 4 previous errors
For more information about this error, try `rustc --explain E0716`.

2
tests/ui/span/send-is-not-static-std-sync-2.stderr
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@ -25,8 +25,6 @@ LL | };
error[E0597]: `x` does not live long enough
--> $DIR/send-is-not-static-std-sync-2.rs:31:25
|
LL | let (_tx, rx) = {
| --- borrow later used here
LL | let x = 1;
| - binding `x` declared here
LL | let (tx, rx) = mpsc::channel();