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doc: clarify allocator invariant #153985

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rust-bors merged 1 commit into from
Mar 18, 2026
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doc: clarify allocator invariant #153985

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7 changes: 7 additions & 0 deletions library/core/src/alloc/mod.rs
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Expand Up @@ -100,6 +100,13 @@ impl fmt::Display for AllocError {
/// A memory block which is [*currently allocated*] may be passed to
/// any method of the allocator that accepts such an argument.
///
/// Additionally, any memory block returned by the allocator must
/// satisfy the allocation invariants described in `core::ptr`.
/// In particular, if a block has base address `p` and size `n`,
/// then `p as usize + n <= usize::MAX` must hold.
///
/// This ensures that pointer arithmetic within the allocation
/// (for example, `ptr.add(len)`) cannot overflow the address space.
/// [*currently allocated*]: #currently-allocated-memory
#[unstable(feature = "allocator_api", issue = "32838")]
#[rustc_const_unstable(feature = "const_heap", issue = "79597")]
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