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array-macro.md

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---
category:       General Utility
description:    `vec![]` but for fixed length arrays
msrv:           1.36.0
---

array-macro

vec![] but for fixed length arrays

Pros:

  • Solid and awesome

Cons:

  • unsafe in macro prevents use with #![forbid(unsafe_code)]
  • Bumps MSRV on patch versions (but so far only for damn good reasons)

Issues

issue severity broke fix desc
#9 🐵 ❗️ high 1.0.4 core::mem::uninitialized is deprecated / undefined behavior
01940637 ❗️ high 1.0.4 1.0.5 Catch-all traits defining length could mess with array!

Audit

version thoroughness understanding rating notes
1.0.5 high high ✔️ positive 01940637 Protection against evil catch-all traits defining length
1.0.4 high high ❔ neutral 01940637 #9 MSRV 1.36.0, MaybeUninit should be safe + sound
1.0.3 high high ❗️ negative #9 Good for the time, but core::mem::uninitialized is technically UB
1.0.2 high high ❗️ negative #9 Good for the time, but core::mem::uninitialized is technically UB
1.0.1 high high ❗️ negative #9 Good for the time, but core::mem::uninitialized is technically UB
1.0.0 high high ❗️ negative #9 Good for the time, but core::mem::uninitialized is technically UB
0.1.2 high high ❗️ negative #9 Good for the time, but core::mem::uninitialized is technically UB

1.0.5

Diff Rating Notes
src\lib.rs ✔️ Protection from evil, internal comments explaining the awkward code
tests\test.rs ✔️ Testing protection against evil

1.0.4

Diff Rating Notes
.gitlab-ci.yml ✔️ MSRV 1.25.0 -> 1.36.0
src\lib.rs ✔️ uninitialized -> MaybeUninit, moved common code out of macro into crate

1.0.3

Diff Rating Notes
.cargo_vcs_info.json ✔️
.gitlab-ci.yml ✔️ MSRV 1.25.0
Cargo.toml ✔️ moved repositories, badge
Cargo.toml.orig ✔️ moved repositories, badge
README.md ✔️ Removed travis badge
src\lib.rs ❗✔️ +local_inner_macros, still uses uninitialized
tests\test.rs ✔️

1.0.2

Diff Rating Notes
src\lib.rs ❗✔️ #[allow(unsafe_code)] in macro, still uses uninitialized
tests\test.rs ✔️ eliminated static mut

1.0.1

Diff Rating Notes
src\lib.rs ❗✔️ ::array_macros::__core:: -> $crate::__core::, still uses uninitialized

1.0.0

Diff Rating Notes
src\lib.rs ❗✔️ str -> String, still uses uninitialized
tests\test.rs ⚠️✔️ Closer scopes, still uses static mut

0.1.2

Decent for the time. Caveats:

  • Doesn't use $crate::
  • Uses core::mem::uninitialized (modern code should use MaybeUninit)

Drop order on panic is "correct" (forward, and only created elements)

Writing vec.position = i before ptr::write looks awkward as heck but is correct.
On the first loop iteration, vec.position = i = 0, so nothing will be dropped if callback(0) panics.
On the second loop iteration, vec.position = i = 1, so the previous element will be dropped if callback(1) panics.
After callback(count-1), no panic can occur before the entire array is assumed initialized, ergo skipping vec.position = i = count-1 isn't a problem.

File Rating Notes
.cargo-ok ✔️
.gitignore ✔️
.travis.yml ✔️ MSRV stable
Cargo.toml ✔️ MIT/Apache-2.0
Cargo.toml.orig ✔️ MIT/Apache-2.0
LICENSE-APACHE ✔️ Apache-2.0
LICENSE-MIT ✔️ MIT
README.md ✔️
src\lib.rs ❗
tests\test.rs ⚠️ static muts could be made atomic for safety
Other Rating Notes
unsafe ❗ uninitialize is technically UB
fs ✔️ None
io ✔️ None
docs ✔️ Good
tests ✔️ Good