Auto merge of - RalfJung:dyn-layout-test, r=RalfJung

Test that we enforce dynamic layout properties (not just static ones of sized prefix)
This commit is contained in:
bors 2020-04-18 07:16:35 +00:00
commit 72667b58b8
3 changed files with 34 additions and 1 deletions
tests/compile-fail
dangling_pointers
unaligned_pointers
validity

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// should find the bug even without these, but gets masked by optimizations
// compile-flags: -Zmiri-disable-validation -Zmiri-disable-stacked-borrows -Zmir-opt-level=0
struct SliceWithHead(u8, [u8]);
fn main() {
let buf = [0u32; 1];
// We craft a wide pointer `*const SliceWithHead` such that the unsized tail is only partially allocated.
// That should be UB, as the reference is not fully dereferencable.
let ptr: *const SliceWithHead = unsafe { std::mem::transmute((&buf, 4usize)) };
// Re-borrow that. This should be UB.
let _ptr = unsafe { &*ptr }; //~ ERROR pointer must be in-bounds at offset 5
}

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// should find the bug even without these, but gets masked by optimizations
// compile-flags: -Zmiri-disable-validation -Zmiri-disable-stacked-borrows -Zmir-opt-level=0
#[repr(align(256))]
#[derive(Debug)]
struct MuchAlign;
fn main() {
let buf = [0u32; 256];
// `buf` is sufficiently aligned for `layout.align` on a `dyn Debug`, but not
// for the actual alignment required by `MuchAlign`.
// We craft a wide reference `&dyn Debug` with the vtable for `MuchAlign`. That should be UB,
// as the reference is not aligned to its dynamic alignment requirements.
let mut ptr = &MuchAlign as &dyn std::fmt::Debug;
// Overwrite the data part of `ptr` so it points to `buf`.
unsafe { (&mut ptr as *mut _ as *mut *const u8).write(&buf as *const _ as *const u8); }
// Re-borrow that. This should be UB.
let _ptr = &*ptr; //~ ERROR accessing memory with alignment 4, but alignment 256 is required
}

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// compile-flags: -Zmir-opt-level=1
// gets masked by optimizations
// compile-flags: -Zmir-opt-level=0
#![feature(rustc_attrs)]
#![allow(unused_attributes)]