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reword Miri validity errors: undefined -> uninitialized #71164

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Merged
merged 3 commits into from
Apr 17, 2020
Merged

reword Miri validity errors: undefined -> uninitialized #71164

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9ee4d1a
reword Miri validity errors: undefined -> uninitialized
RalfJung Apr 15, 2020
0d01ce6
switch back to 'bytes'
RalfJung Apr 16, 2020
69423bf
test fast path offset reporting
RalfJung Apr 16, 2020
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17 changes: 11 additions & 6 deletions src/librustc_mir/interpret/validity.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -322,7 +322,11 @@ impl<'rt, 'mir, 'tcx, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, 'tcx, M
let value = self.ecx.read_immediate(value)?;
// Handle wide pointers.
// Check metadata early, for better diagnostics
let place = try_validation!(self.ecx.ref_to_mplace(value), "undefined pointer", self.path);
let place = try_validation!(
self.ecx.ref_to_mplace(value),
format_args!("uninitialized {}", kind),
self.path
);
if place.layout.is_unsized() {
self.check_wide_ptr_meta(place.meta, place.layout)?;
}
Expand All @@ -334,7 +338,7 @@ impl<'rt, 'mir, 'tcx, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, 'tcx, M
format_args!("invalid {} metadata: {}", kind, msg),
self.path
),
_ => bug!("Unexpected error during ptr size_and_align_of: {}", err),
_ => bug!("unexpected error during ptr size_and_align_of: {}", err),
},
};
let (size, align) = size_and_align
Expand Down Expand Up @@ -477,10 +481,11 @@ impl<'rt, 'mir, 'tcx, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, 'tcx, M
}
ty::RawPtr(..) => {
// We are conservative with undef for integers, but try to
// actually enforce our current rules for raw pointers.
// actually enforce the strict rules for raw pointers (mostly because
// that lets us re-use `ref_to_mplace`).
let place = try_validation!(
self.ecx.ref_to_mplace(self.ecx.read_immediate(value)?),
"undefined pointer",
"uninitialized raw pointer",
self.path
);
if place.layout.is_unsized() {
Expand Down Expand Up @@ -776,14 +781,14 @@ impl<'rt, 'mir, 'tcx, M: Machine<'mir, 'tcx>> ValueVisitor<'mir, 'tcx, M>
// For some errors we might be able to provide extra information
match err.kind {
err_ub!(InvalidUndefBytes(Some(ptr))) => {
// Some byte was undefined, determine which
// Some byte was uninitialized, determine which
// element that byte belongs to so we can
// provide an index.
let i = usize::try_from(ptr.offset.bytes() / layout.size.bytes())
.unwrap();
self.path.push(PathElem::ArrayElem(i));

throw_validation_failure!("undefined bytes", self.path)
throw_validation_failure!("uninitialized bytes", self.path)
}
// Other errors shouldn't be possible
_ => return Err(err),
Expand Down
65 changes: 65 additions & 0 deletions src/test/ui/consts/const-eval/ub-int-array.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,65 @@
#![feature(const_transmute)]
#![allow(const_err)] // make sure we cannot allow away the errors tested here

//! Test the "array of int" fast path in validity checking, and in particular whether it
//! points at the right array element.

use std::mem;

#[repr(C)]
union MaybeUninit<T: Copy> {
uninit: (),
init: T,
}

const UNINIT_INT_0: [u32; 3] = unsafe {
//~^ ERROR it is undefined behavior to use this value
//~| type validation failed: encountered uninitialized bytes at [0]
[
MaybeUninit { uninit: () }.init,
1,
2,
]
};
const UNINIT_INT_1: [u32; 3] = unsafe {
//~^ ERROR it is undefined behavior to use this value
//~| type validation failed: encountered uninitialized bytes at [1]
mem::transmute(
[
0u8,
0u8,
0u8,
0u8,
1u8,
MaybeUninit { uninit: () }.init,
1u8,
1u8,
2u8,
2u8,
MaybeUninit { uninit: () }.init,
2u8,
]
)
};
const UNINIT_INT_2: [u32; 3] = unsafe {
//~^ ERROR it is undefined behavior to use this value
//~| type validation failed: encountered uninitialized bytes at [2]
mem::transmute(
[
0u8,
0u8,
0u8,
0u8,
1u8,
1u8,
1u8,
1u8,
2u8,
2u8,
2u8,
MaybeUninit { uninit: () }.init,
]
)
};

fn main() {}
45 changes: 45 additions & 0 deletions src/test/ui/consts/const-eval/ub-int-array.stderr
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Original file line number Diff line number Diff line change
@@ -0,0 +1,45 @@
error[E0080]: it is undefined behavior to use this value
--> $DIR/ub-int-array.rs:15:1
|
LL | / const UNINIT_INT_0: [u32; 3] = unsafe {
LL | |
LL | |
LL | | [
... |
LL | | ]
LL | | };
| |__^ type validation failed: encountered uninitialized bytes at [0]
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@oli-obk oli-obk Apr 16, 2020 •
edited
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Maybe we should dump the memory of constants at some point and have diagnostics point into them (but in general it's useless for validation to point to the entire constant's span, just pointing to the name should suffice)

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Yeah it's not great -- but also pre-existing.

|
= note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.

error[E0080]: it is undefined behavior to use this value
--> $DIR/ub-int-array.rs:24:1
|
LL | / const UNINIT_INT_1: [u32; 3] = unsafe {
LL | |
LL | |
LL | | mem::transmute(
... |
LL | | )
LL | | };
| |__^ type validation failed: encountered uninitialized bytes at [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 rustc repository if you believe it should not be considered undefined behavior.

error[E0080]: it is undefined behavior to use this value
--> $DIR/ub-int-array.rs:44:1
|
LL | / const UNINIT_INT_2: [u32; 3] = unsafe {
LL | |
LL | |
LL | | mem::transmute(
... |
LL | | )
LL | | };
| |__^ type validation failed: encountered uninitialized bytes at [2]
|
= note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.

error: aborting due to 3 previous errors

For more information about this error, try `rustc --explain E0080`.
4 changes: 2 additions & 2 deletions src/test/ui/consts/const-eval/ub-ref.rs
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Expand Up @@ -6,11 +6,11 @@ use std::mem;

const UNALIGNED: &u16 = unsafe { mem::transmute(&[0u8; 4]) };
//~^ ERROR it is undefined behavior to use this value
//~^^ type validation failed: encountered an unaligned reference (required 2 byte alignment but found 1)
//~| type validation failed: encountered an unaligned reference (required 2 byte alignment but found 1)

const UNALIGNED_BOX: Box<u16> = unsafe { mem::transmute(&[0u8; 4]) };
//~^ ERROR it is undefined behavior to use this value
//~^^ type validation failed: encountered an unaligned box (required 2 byte alignment but found 1)
//~| type validation failed: encountered an unaligned box (required 2 byte alignment but found 1)

const NULL: &u16 = unsafe { mem::transmute(0usize) };
//~^ ERROR it is undefined behavior to use this value
Expand Down
4 changes: 2 additions & 2 deletions src/test/ui/consts/const-eval/ub-wide-ptr.stderr
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Expand Up @@ -62,7 +62,7 @@ LL | |
LL | | let uninit_len = MaybeUninit::<usize> { uninit: () };
LL | | mem::transmute((42, uninit_len))
LL | | };
| |__^ type validation failed: encountered undefined pointer
| |__^ type validation failed: encountered uninitialized reference
|
= note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.

Expand Down Expand Up @@ -130,7 +130,7 @@ LL | |
LL | | let uninit_len = MaybeUninit::<usize> { uninit: () };
LL | | mem::transmute((42, uninit_len))
LL | | };
| |__^ type validation failed: encountered undefined pointer
| |__^ type validation failed: encountered uninitialized raw 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 rustc repository if you believe it should not be considered undefined behavior.

Expand Down
2 changes: 1 addition & 1 deletion src/test/ui/consts/const-eval/union-ice.stderr
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Expand Up @@ -27,7 +27,7 @@ LL | | unsafe { UNION.field3 },
... |
LL | | a: 42,
LL | | };
| |__^ type validation failed: encountered undefined bytes at .b[1]
| |__^ type validation failed: encountered uninitialized bytes at .b[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 rustc repository if you believe it should not be considered undefined behavior.

Expand Down