test for detecting bad data inside trait objects / slices

Author: RalfJung

src/test/ui/union-ub-fat-ptr.rs

@@ -13,6 +13,11 @@
 // normalize-stderr-test "allocation \d+" -> "allocation N"
 // normalize-stderr-test "size \d+" -> "size N"
 
+union BoolTransmute {
+  val: u8,
+  bl: bool,
+}
+
 #[repr(C)]
 #[derive(Copy, Clone)]
 struct SliceRepr {
@@ -63,34 +68,43 @@ union DynTransmute {
 }
 
 trait Trait {}
+impl Trait for bool {}
 
 // OK
 const A: &str = unsafe { SliceTransmute { repr: SliceRepr { ptr: &42, len: 1 } }.str};
-// bad
+// bad str
 const B: &str = unsafe { SliceTransmute { repr: SliceRepr { ptr: &42, len: 999 } }.str};
 //~^ ERROR this constant likely exhibits undefined behavior
-// bad
+// bad str
 const C: &str = unsafe { SliceTransmute { bad: BadSliceRepr { ptr: &42, len: &3 } }.str};
 //~^ ERROR this constant likely exhibits undefined behavior
 
 // OK
 const A2: &[u8] = unsafe { SliceTransmute { repr: SliceRepr { ptr: &42, len: 1 } }.slice};
-// bad
+// bad slice
 const B2: &[u8] = unsafe { SliceTransmute { repr: SliceRepr { ptr: &42, len: 999 } }.slice};
 //~^ ERROR this constant likely exhibits undefined behavior
-// bad
+// bad slice
 const C2: &[u8] = unsafe { SliceTransmute { bad: BadSliceRepr { ptr: &42, len: &3 } }.slice};
 //~^ ERROR this constant likely exhibits undefined behavior
 
-// bad
+// bad trait object
 const D: &Trait = unsafe { DynTransmute { repr: DynRepr { ptr: &92, vtable: &3 } }.rust};
 //~^ ERROR this constant likely exhibits undefined behavior
-// bad
+// bad trait object
 const E: &Trait = unsafe { DynTransmute { repr2: DynRepr2 { ptr: &92, vtable: &3 } }.rust};
 //~^ ERROR this constant likely exhibits undefined behavior
-// bad
+// bad trait object
 const F: &Trait = unsafe { DynTransmute { bad: BadDynRepr { ptr: &92, vtable: 3 } }.rust};
 //~^ ERROR this constant likely exhibits undefined behavior
 
+// bad data *inside* the trait object
+const G: &Trait = &unsafe { BoolTransmute { val: 3 }.bl };
+//~^ ERROR this constant likely exhibits undefined behavior
+
+// bad data *inside* the slice
+const H: &[bool] = &[unsafe { BoolTransmute { val: 3 }.bl }];
+//~^ ERROR this constant likely exhibits undefined behavior
+
 fn main() {
 }

src/test/ui/union-ub-fat-ptr.stderr

@@ -1,59 +1,75 @@
 error[E0080]: this constant likely exhibits undefined behavior
-  --> $DIR/union-ub-fat-ptr.rs:70:1
+  --> $DIR/union-ub-fat-ptr.rs:76:1
    |
 LL | const B: &str = unsafe { SliceTransmute { repr: SliceRepr { ptr: &42, len: 999 } }.str};
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ memory access at offset N, outside bounds of allocation N which has size N
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
 
 error[E0080]: this constant likely exhibits undefined behavior
-  --> $DIR/union-ub-fat-ptr.rs:73:1
+  --> $DIR/union-ub-fat-ptr.rs:79:1
    |
 LL | const C: &str = unsafe { SliceTransmute { bad: BadSliceRepr { ptr: &42, len: &3 } }.str};
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered length is not a valid integer
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
 
 error[E0080]: this constant likely exhibits undefined behavior
-  --> $DIR/union-ub-fat-ptr.rs:79:1
+  --> $DIR/union-ub-fat-ptr.rs:85:1
    |
 LL | const B2: &[u8] = unsafe { SliceTransmute { repr: SliceRepr { ptr: &42, len: 999 } }.slice};
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ memory access at offset N, outside bounds of allocation N which has size N
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
 
 error[E0080]: this constant likely exhibits undefined behavior
-  --> $DIR/union-ub-fat-ptr.rs:82:1
+  --> $DIR/union-ub-fat-ptr.rs:88:1
    |
 LL | const C2: &[u8] = unsafe { SliceTransmute { bad: BadSliceRepr { ptr: &42, len: &3 } }.slice};
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered length is not a valid integer
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
 
 error[E0080]: this constant likely exhibits undefined behavior
-  --> $DIR/union-ub-fat-ptr.rs:86:1
+  --> $DIR/union-ub-fat-ptr.rs:92:1
    |
 LL | const D: &Trait = unsafe { DynTransmute { repr: DynRepr { ptr: &92, vtable: &3 } }.rust};
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ tried to access memory with alignment N, but alignment N is required
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
 
 error[E0080]: this constant likely exhibits undefined behavior
-  --> $DIR/union-ub-fat-ptr.rs:89:1
+  --> $DIR/union-ub-fat-ptr.rs:95:1
    |
 LL | const E: &Trait = unsafe { DynTransmute { repr2: DynRepr2 { ptr: &92, vtable: &3 } }.rust};
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ a memory access tried to interpret some bytes as a pointer
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
 
 error[E0080]: this constant likely exhibits undefined behavior
-  --> $DIR/union-ub-fat-ptr.rs:92:1
+  --> $DIR/union-ub-fat-ptr.rs:98:1
    |
 LL | const F: &Trait = unsafe { DynTransmute { bad: BadDynRepr { ptr: &92, vtable: 3 } }.rust};
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered vtable address is not a pointer
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
 
-error: aborting due to 7 previous errors
+error[E0080]: this constant likely exhibits undefined behavior
+  --> $DIR/union-ub-fat-ptr.rs:102:1
+   |
+LL | const G: &Trait = &unsafe { BoolTransmute { val: 3 }.bl };
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 3 at .data_ptr, but expected something in the range 0..=1
+   |
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+
+error[E0080]: this constant likely exhibits undefined behavior
+  --> $DIR/union-ub-fat-ptr.rs:106:1
+   |
+LL | const H: &[bool] = &[unsafe { BoolTransmute { val: 3 }.bl }];
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 3 at .data_ptr[0], but expected something in the range 0..=1
+   |
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+
+error: aborting due to 9 previous errors
 
 For more information about this error, try `rustc --explain E0080`.