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Auto merge of #3896 - RalfJung:ptr_offset_unsigned_overflow, r=RalfJung

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ptr_offset_unsigned_overflow: extend test

Test that indeed, the signed version works before the unsigned version is UB.
This commit is contained in:
bors 2024-09-17 17:25:43 +00:00
commit 62ccf6a434
2 changed files with 6 additions and 5 deletions
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7
src/tools/miri/tests/fail/intrinsics/ptr_offset_unsigned_overflow.rs
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@ -1,7 +1,8 @@
fn main() {
let x = &[0i32; 2];
let x = x.as_ptr().wrapping_add(1);
// If the `!0` is interpreted as `isize`, it is just `-1` and hence harmless.
// However, this is unsigned arithmetic, so really this is `usize::MAX` and hence UB.
unsafe { x.byte_add(!0).read() }; //~ERROR: does not fit in an `isize`
// If `usize::MAX` is interpreted as `isize`, it is just `-1` and hence harmless.
let _ = unsafe { x.byte_offset(usize::MAX as isize) };
// However, `byte_add` uses unsigned arithmetic, so really this is `usize::MAX` and hence UB.
let _ = unsafe { x.byte_add(usize::MAX) }; //~ERROR: does not fit in an `isize`
}

4
src/tools/miri/tests/fail/intrinsics/ptr_offset_unsigned_overflow.stderr
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@ -1,8 +1,8 @@
error: Undefined Behavior: overflowing pointer arithmetic: the total offset in bytes does not fit in an `isize`
--> tests/fail/intrinsics/ptr_offset_unsigned_overflow.rs:LL:CC
|
LL | unsafe { x.byte_add(!0).read() };
| ^^^^^^^^^^^^^^ overflowing pointer arithmetic: the total offset in bytes does not fit in an `isize`
LL | let _ = unsafe { x.byte_add(usize::MAX) };
| ^^^^^^^^^^^^^^^^^^^^^^ overflowing pointer arithmetic: the total offset in bytes does not fit in an `isize`
|
= 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