rust/library/alloc/tests/lib.rs

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alloc_system: don’t assume MIN_ALIGN for small sizes, fix #45955 The GNU C library (glibc) is documented to always allocate with an alignment of at least 8 or 16 bytes, on 32-bit or 64-bit platforms: https://www.gnu.org/software/libc/manual/html_node/Aligned-Memory-Blocks.html This matches our use of `MIN_ALIGN` before this commit. However, even when libc is glibc, the program might be linked with another allocator that redefines the `malloc` symbol and friends. (The `alloc_jemalloc` crate does, in some cases.) So `alloc_system` doesn’t know which allocator it calls, and needs to be conservative in assumptions it makes. The C standard says: https://port70.net/%7Ensz/c/c11/n1570.html#7.22.3 > The pointer returned if the allocation succeeds is suitably aligned > so that it may be assigned to a pointer to any type of object > with a fundamental alignment requirement https://port70.net/~nsz/c/c11/n1570.html#6.2.8p2 > A fundamental alignment is represented by an alignment less than > or equal to the greatest alignment supported by the implementation > in all contexts, which is equal to `_Alignof (max_align_t)`. `_Alignof (max_align_t)` depends on the ABI and doesn’t seem to have a clear definition, but it seems to match our `MIN_ALIGN` in practice. However, the size of objects is rounded up to the next multiple of their alignment (since that size is also the stride used in arrays). Conversely, the alignment of a non-zero-size object is at most its size. So for example it seems ot be legal for `malloc(8)` to return a pointer that’s only 8-bytes-aligned, even if `_Alignof (max_align_t)` is 16.
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#![feature(allocator_api)]
#![feature(box_syntax)]
#![feature(cow_is_borrowed)]
#![feature(const_cow_is_borrowed)]
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#![feature(drain_filter)]
#![feature(exact_size_is_empty)]
#![feature(new_uninit)]
#![feature(pattern)]
#![feature(str_split_once)]
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#![feature(trusted_len)]
#![feature(try_reserve)]
#![feature(unboxed_closures)]
#![feature(associated_type_bounds)]
#![feature(binary_heap_into_iter_sorted)]
#![feature(binary_heap_drain_sorted)]
#![feature(slice_ptr_get)]
#![feature(split_inclusive)]
#![feature(binary_heap_retain)]
#![feature(deque_range)]
#![feature(inplace_iteration)]
#![feature(iter_map_while)]
#![feature(int_bits_const)]
#![feature(vecdeque_binary_search)]
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use std::collections::hash_map::DefaultHasher;
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use std::hash::{Hash, Hasher};
mod arc;
mod binary_heap;
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mod borrow;
mod boxed;
mod btree_set_hash;
mod cow_str;
mod fmt;
alloc_system: don’t assume MIN_ALIGN for small sizes, fix #45955 The GNU C library (glibc) is documented to always allocate with an alignment of at least 8 or 16 bytes, on 32-bit or 64-bit platforms: https://www.gnu.org/software/libc/manual/html_node/Aligned-Memory-Blocks.html This matches our use of `MIN_ALIGN` before this commit. However, even when libc is glibc, the program might be linked with another allocator that redefines the `malloc` symbol and friends. (The `alloc_jemalloc` crate does, in some cases.) So `alloc_system` doesn’t know which allocator it calls, and needs to be conservative in assumptions it makes. The C standard says: https://port70.net/%7Ensz/c/c11/n1570.html#7.22.3 > The pointer returned if the allocation succeeds is suitably aligned > so that it may be assigned to a pointer to any type of object > with a fundamental alignment requirement https://port70.net/~nsz/c/c11/n1570.html#6.2.8p2 > A fundamental alignment is represented by an alignment less than > or equal to the greatest alignment supported by the implementation > in all contexts, which is equal to `_Alignof (max_align_t)`. `_Alignof (max_align_t)` depends on the ABI and doesn’t seem to have a clear definition, but it seems to match our `MIN_ALIGN` in practice. However, the size of objects is rounded up to the next multiple of their alignment (since that size is also the stride used in arrays). Conversely, the alignment of a non-zero-size object is at most its size. So for example it seems ot be legal for `malloc(8)` to return a pointer that’s only 8-bytes-aligned, even if `_Alignof (max_align_t)` is 16.
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mod heap;
mod linked_list;
mod rc;
mod slice;
mod str;
mod string;
mod vec;
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mod vec_deque;
fn hash<T: Hash>(t: &T) -> u64 {
let mut s = DefaultHasher::new();
t.hash(&mut s);
s.finish()
}
// FIXME: Instantiated functions with i128 in the signature is not supported in Emscripten.
// See https://github.com/kripken/emscripten-fastcomp/issues/169
#[cfg(not(target_os = "emscripten"))]
#[test]
fn test_boxed_hasher() {
let ordinary_hash = hash(&5u32);
let mut hasher_1 = Box::new(DefaultHasher::new());
5u32.hash(&mut hasher_1);
assert_eq!(ordinary_hash, hasher_1.finish());
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let mut hasher_2 = Box::new(DefaultHasher::new()) as Box<dyn Hasher>;
5u32.hash(&mut hasher_2);
assert_eq!(ordinary_hash, hasher_2.finish());
}