feat(multitude): Introduce Alloc<T> and reintroduce Rc<T> (#521)

- Arenas no longer return simple references (&mut T), then now instead
return `Alloc<T>`. This makes it so these allocated objects can be
dropped promptly instead of at chunk retirement. This in turn makes it
possible for the T being allocated to not needing to be `Send`. And it
simplifies the internal logic by eliminating the complexities around
deferred drop logic.

- Now that underlying implementations issues have been addressed,
reintroduce Rc<T>.

- Shave a few instructions from some arena allocation functions.

Co-authored-by: Martin Taillefer <mataille@microsoft.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: 3 people

.spelling

@@ -10,6 +10,7 @@
 2×
 5xx
 =
+>=
 ABA
 ABI
 ACLs
@@ -317,6 +318,7 @@ end_offset
 entry_offset
 enum
 enums
+escapable
 evaluator
 ffi
 fhl-scus4-app-win
@@ -527,6 +529,7 @@ submodules
 substring
 subtrait
 sudo
+superset
 supertrait
 supertraits
 sys

Cargo.lock

@@ -73,7 +73,7 @@ fundle_macros = { path = "crates/fundle_macros", default-features = false, versi
 fundle_macros_impl = { path = "crates/fundle_macros_impl", default-features = false, version = "0.3.3" }
 http_extensions = { path = "crates/http_extensions", default-features = false, version = "0.6.3" }
 layered = { path = "crates/layered", default-features = false, version = "0.3.4" }
-multitude = { path = "crates/multitude", default-features = false, version = "0.4.1" }
+multitude = { path = "crates/multitude", default-features = false, version = "0.5.0" }
 ohno = { path = "crates/ohno", default-features = false, version = "0.3.7" }
 ohno_macros = { path = "crates/ohno_macros", default-features = false, version = "0.3.4" }
 recoverable = { path = "crates/recoverable", default-features = false, version = "0.1.6" }
@@ -135,6 +135,7 @@ jiff = { version = "0.2.21", default-features = false }
 libc = { version = "0.2.178", default-features = false }
 loom = { version = "0.7.2", default-features = false }
 many_cpus = { version = "2.1.0", default-features = false }
+mimalloc = { version = "0.1.52", default-features = false }
 mockall = { version = "0.14.0", default-features = false }
 moka = { version = "0.12.14", default-features = false }
 mutants = { version = "0.0.3", default-features = false }

Cargo.toml

@@ -3,7 +3,7 @@
 
 [package]
 name = "multitude"
-version = "0.4.1"
+version = "0.5.0"
 description = "Fast and flexible arena allocator."
 readme = "README.md"
 keywords = ["arena", "memory", "allocator", "bump"]
@@ -77,6 +77,7 @@ bolero = { workspace = true, features = ["std"] }
 # but does not itself activate that feature on `bolero-engine`.
 bumpalo = { workspace = true, features = ["collections"] }
 criterion = { workspace = true }
+mimalloc = { workspace = true }
 mutants = { workspace = true }
 serde_json = { workspace = true }
 
@@ -104,6 +105,14 @@ harness = false
 name = "criterion_arc_array"
 harness = false
 
+[[bench]]
+name = "criterion_rc_array"
+harness = false
+
+[[bench]]
+name = "criterion_arena_vs_allocator"
+harness = false
+
 # Callgrind benches require Linux (Valgrind). The bench files are gated to compile
 # to a no-op on non-Linux targets, but the [[bench]] entry itself cannot be
 # cfg-gated, so it is unconditional here.
@@ -119,6 +128,10 @@ harness = false
 name = "gungraun_arc_array"
 harness = false
 
+[[bench]]
+name = "gungraun_rc_array"
+harness = false
+
 [[example]]
 name = "multitude_basic"