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Auto merge of rust-lang#94860 - Dylan-DPC:rollup-n06j8h6, r=Dylan-DPC
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Rollup of 7 pull requests

Successful merges:

 - rust-lang#87618 (Add missing documentation for std::char types)
 - rust-lang#94769 (Collapse blanket and auto-trait impls by default)
 - rust-lang#94798 (`parse_tt` refactorings)
 - rust-lang#94818 (Rename `IntoFuture::Future` to `IntoFuture::IntoFuture`)
 - rust-lang#94827 (CTFE/Miri: detect out-of-bounds pointers in offset_from)
 - rust-lang#94838 (Make float parsing docs more comprehensive)
 - rust-lang#94839 (Suggest using double colon when a struct field type include single colon)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
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@bors
bors committed Mar 11, 2022
2 parents 335ffbf + 298c9a0 commit 2c6a29a
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Showing 16 changed files with 334 additions and 183 deletions.
80 changes: 42 additions & 38 deletions compiler/rustc_const_eval/src/interpret/intrinsics.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -307,53 +307,57 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
self.write_pointer(offset_ptr, dest)?;
}
sym::ptr_offset_from => {
let a = self.read_immediate(&args[0])?.to_scalar()?;
let b = self.read_immediate(&args[1])?.to_scalar()?;
let a = self.read_pointer(&args[0])?;
let b = self.read_pointer(&args[1])?;

// Special case: if both scalars are *equal integers*
// and not null, we pretend there is an allocation of size 0 right there,
// and their offset is 0. (There's never a valid object at null, making it an
// exception from the exception.)
// This is the dual to the special exception for offset-by-0
// in the inbounds pointer offset operation (see the Miri code, `src/operator.rs`).
//
// Control flow is weird because we cannot early-return (to reach the
// `go_to_block` at the end).
let done = if let (Ok(a), Ok(b)) = (a.try_to_int(), b.try_to_int()) {
let a = a.try_to_machine_usize(*self.tcx).unwrap();
let b = b.try_to_machine_usize(*self.tcx).unwrap();
if a == b && a != 0 {
// in the inbounds pointer offset operation (see `ptr_offset_inbounds` below).
match (self.memory.ptr_try_get_alloc(a), self.memory.ptr_try_get_alloc(b)) {
(Err(a), Err(b)) if a == b && a != 0 => {
// Both are the same non-null integer.
self.write_scalar(Scalar::from_machine_isize(0, self), dest)?;
true
} else {
false
}
} else {
false
};

if !done {
// General case: we need two pointers.
let a = self.scalar_to_ptr(a);
let b = self.scalar_to_ptr(b);
let (a_alloc_id, a_offset, _) = self.memory.ptr_get_alloc(a)?;
let (b_alloc_id, b_offset, _) = self.memory.ptr_get_alloc(b)?;
if a_alloc_id != b_alloc_id {
throw_ub_format!(
"ptr_offset_from cannot compute offset of pointers into different \
allocations.",
);
(Err(offset), _) | (_, Err(offset)) => {
throw_ub!(DanglingIntPointer(offset, CheckInAllocMsg::OffsetFromTest));
}
(Ok((a_alloc_id, a_offset, _)), Ok((b_alloc_id, b_offset, _))) => {
// Both are pointers. They must be into the same allocation.
if a_alloc_id != b_alloc_id {
throw_ub_format!(
"ptr_offset_from cannot compute offset of pointers into different \
allocations.",
);
}
// And they must both be valid for zero-sized accesses ("in-bounds or one past the end").
self.memory.check_ptr_access_align(
a,
Size::ZERO,
Align::ONE,
CheckInAllocMsg::OffsetFromTest,
)?;
self.memory.check_ptr_access_align(
b,
Size::ZERO,
Align::ONE,
CheckInAllocMsg::OffsetFromTest,
)?;

// Compute offset.
let usize_layout = self.layout_of(self.tcx.types.usize)?;
let isize_layout = self.layout_of(self.tcx.types.isize)?;
let a_offset = ImmTy::from_uint(a_offset.bytes(), usize_layout);
let b_offset = ImmTy::from_uint(b_offset.bytes(), usize_layout);
let (val, _overflowed, _ty) =
self.overflowing_binary_op(BinOp::Sub, &a_offset, &b_offset)?;
let pointee_layout = self.layout_of(substs.type_at(0))?;
let val = ImmTy::from_scalar(val, isize_layout);
let size = ImmTy::from_int(pointee_layout.size.bytes(), isize_layout);
self.exact_div(&val, &size, dest)?;
}
let usize_layout = self.layout_of(self.tcx.types.usize)?;
let isize_layout = self.layout_of(self.tcx.types.isize)?;
let a_offset = ImmTy::from_uint(a_offset.bytes(), usize_layout);
let b_offset = ImmTy::from_uint(b_offset.bytes(), usize_layout);
let (val, _overflowed, _ty) =
self.overflowing_binary_op(BinOp::Sub, &a_offset, &b_offset)?;
let pointee_layout = self.layout_of(substs.type_at(0))?;
let val = ImmTy::from_scalar(val, isize_layout);
let size = ImmTy::from_int(pointee_layout.size.bytes(), isize_layout);
self.exact_div(&val, &size, dest)?;
}
}

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6 changes: 3 additions & 3 deletions compiler/rustc_const_eval/src/interpret/memory.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -388,9 +388,9 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
CheckInAllocMsg::DerefTest | CheckInAllocMsg::MemoryAccessTest => {
AllocCheck::Dereferenceable
}
CheckInAllocMsg::PointerArithmeticTest | CheckInAllocMsg::InboundsTest => {
AllocCheck::Live
}
CheckInAllocMsg::PointerArithmeticTest
| CheckInAllocMsg::OffsetFromTest
| CheckInAllocMsg::InboundsTest => AllocCheck::Live,
};
let (size, align) = self.get_size_and_align(alloc_id, check)?;
Ok((size, align, ()))
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