Justus Klausecker ce3f254526 std.heap.ArenaAllocator: do not cmpxchg in hot path when it would be a noop ...

The cmpxchg is there to recover alignment padding that isn't needed (which
can only be determined after the fetch-and-add that reserves it as allocated
memory). As cmpxchg tends to be a very expensive operation, it is actually
faster to introduce an additional branch here that checks if the cmpxchg
would be a noop (because all of the reserved alignment padding was in fact
necessary) and skips it if that's the case.

This does not measurably regress performance if the arena is only accessed
by a single thread and yields slight performance benefits for multi-threaded
usage. If the arena is commonly used for unaligned allocations, the perf
benefits are quite significant.

Co-authored-by: Jacob Young <amazingjacob@gmail.com>

2026-04-02 23:00:26 +02:00

..

Build

Merge pull request 'add an ast smith' (#31635) from gooncreeper/zig:ast-smith into master

2026-04-02 15:41:05 +02:00

builtin

Add lr and sp clobbers for arm/thumb

2026-02-20 01:16:33 +01:00

c

std.os.linux: add explicit backing type to packed structs in extern types

2026-03-12 22:33:03 +01:00

compress

implement proper deflate flush semantics

2026-03-11 02:28:19 +01:00

crypto

crypto.base64: use "-" instead of "+" character in URL-safe mode

2026-03-29 09:33:22 +02:00

debug

Merge pull request 'std.heap.ArenaAllocator: decrease fuzz test workload per run' (#31596) from justusk/zig:fuzz-arena-2 into master

2026-04-02 15:57:41 +02:00

dwarf

fix compiler ftbfs from std.macho and std.dwarf changes

2025-09-30 13:44:51 +01:00

fmt

all: replace all @Type usages

2025-11-22 22:42:38 +00:00

fs

std: make file locking tests use io not threads

2026-04-01 02:54:25 -07:00

hash

Make benchmarking use std.Io.Clock.awake for timing (#31553)

2026-03-18 21:00:08 +01:00

heap

std.heap.ArenaAllocator: do not cmpxchg in hot path when it would be a noop

2026-04-02 23:00:26 +02:00

http

Package.Fetch: bump redirect buffer size

2026-03-27 08:42:02 +01:00

Io

handle EROFS in create/open file

2026-04-02 15:05:31 +02:00

json

Merge pull request 'rework fuzz testing to be smith based' (#31205) from gooncreeper/zig:integrated-smith into master

2026-02-25 20:23:36 +01:00

math

std.math.pow: organise and add special case tests

2026-03-16 15:42:35 +08:00

mem

std: fix sentinel handling in Allocator interface

2026-03-25 10:50:24 +01:00

meta

all: replace all @Type usages

2025-11-22 22:42:38 +00:00

os

std.os.linux: add set_tid_address

2026-03-31 14:47:22 -05:00

posix

std.posix: remove close function

2026-02-11 23:37:31 +01:00

process

Io.Dispatch: introduce grand central dispatch io impl

2026-02-13 12:29:40 -05:00

Random

Make benchmarking use std.Io.Clock.awake for timing (#31553)

2026-03-18 21:00:08 +01:00

sort

std.sort.pdq: fix out-of-bounds access in partialInsertionSort (#25253)

2025-09-17 19:54:15 -07:00

tar

Use / as path separator when writing tar files

2026-03-08 02:10:00 +01:00

Target

misc: Add allegrex CPU & features, run tool, update semver

2026-03-21 19:39:04 -04:00

testing

add an ast smith

2026-03-25 17:27:18 -04:00

time

removed reduntant @as() from switch in getDaysInMonth

2026-02-05 21:58:35 +01:00

tz

…

unicode

Make benchmarking use std.Io.Clock.awake for timing (#31553)

2026-03-18 21:00:08 +01:00

valgrind

Remove numerous things deprecated during the 0.14 release cycle

2025-07-11 08:17:43 +02:00

zig

Merge pull request 'add an ast smith' (#31635) from gooncreeper/zig:ast-smith into master

2026-04-02 15:41:05 +02:00

zon

std: update for language changes

2026-03-10 10:38:50 +00:00

array_hash_map.zig

update deprecated ArrayListUnmanaged usage (#25958)

2025-11-20 14:46:23 -08:00

array_list.zig

Simplify std.ArrayList.replaceRange and std.ArrayList.replaceRangeAssumeCapacity (#31710)

2026-04-02 15:11:24 +02:00

ascii.zig

feat(std.ascii): add boundedOrderIgnoreCaseZ

2026-01-17 21:42:38 +01:00

atomic.zig

Merge pull request 'std.heap.ArenaAllocator: add fuzz test + some optimizations' (#31407) from justusk/zig:fuzz-arena into master

2026-03-11 03:00:07 +01:00

base64.zig

Base64DecoderWithIgnore.calcSizeUpperBound cannot return an error (#25834)

2025-11-07 08:16:34 +01:00

bit_set.zig

bit_set: specify the backing integer for IntegerBitSet, allowing it to be used in extern structs

2026-03-16 19:07:13 +01:00

BitStack.zig

std.ArrayList: make unmanaged the default

2025-08-11 15:52:49 -07:00

buf_map.zig

…

buf_set.zig

…

Build.zig

allow specifying mode in --debug-rt

2026-02-13 17:58:09 -05:00

builtin.zig

std: update for language changes

2026-03-10 10:38:50 +00:00

c.zig

std.Io.Dir: add resolve_beneath flag and implement for freebsd,macos

2026-03-27 01:23:04 -07:00

coff.zig

std: replace usages of std.mem.indexOf with std.mem.find

2025-12-05 14:31:27 +01:00

compress.zig

std.compress: rework flate to new I/O API

2025-07-31 22:10:11 -07:00

crypto.zig

crypto: Allow arbitrary types for secureZeroes

2026-02-13 17:07:03 +01:00

debug.zig

Merge pull request 'rework fuzz testing to be smith based' (#31205) from gooncreeper/zig:integrated-smith into master

2026-02-25 20:23:36 +01:00

deque.zig

rework fuzz testing to be smith based

2026-02-13 22:12:19 -05:00

DoublyLinkedList.zig

*LinkedList.remove() assumes node is in the list

2025-10-25 21:10:02 -07:00

dwarf.zig

…

dynamic_library.zig

std: move GetFinalPathNameByHandle to Io.Threaded

2026-02-04 16:27:13 -08:00

elf.zig

std: work around language changes

2026-03-10 10:26:07 +00:00

enums.zig

fix: inline to propagate comptime-ness to call site

2026-03-03 21:10:30 +01:00

fmt.zig

std: replace usages of std.mem.indexOf with std.mem.find

2025-12-05 14:31:27 +01:00

fs.zig

std: find a better home for the "preopens" concept

2026-01-08 05:06:31 +01:00

gpu.zig

remove std.gpu.(binding|location)

2025-12-22 10:00:35 -08:00

hash_map.zig

compiler,std: various little fixes

2026-03-10 10:26:14 +00:00

hash.zig

all: replace all @Type usages

2025-11-22 22:42:38 +00:00

heap.zig

std.Target: add psp os

2026-03-21 02:56:24 -04:00

http.zig

update all occurrences of std.fs.File to std.Io.File

2025-12-23 22:15:07 -08:00

Io.zig

std.Io: move File.CreateFlags to Dir.CreateFileOptions

2026-03-27 01:23:04 -07:00

json.zig

std.Io: delete GenericReader

2025-08-29 17:14:26 -07:00

leb128.zig

std.Io: delete GenericReader

2025-08-29 17:14:26 -07:00

log.zig

std.Threaded: replace console kernel32 functions with ntdll

2026-02-05 07:41:25 -05:00

macho.zig

std: update for language changes

2026-03-10 10:38:50 +00:00

math.zig

even tighter return type for std.math.sign (#31485)

2026-03-17 02:10:27 +01:00

mem.zig

Merge pull request 'std: add mem.absorbSentinel(), fix sentinel handling in Allocator interface' (#31611) from ifreund/zig:absorb-sent into master

2026-04-02 15:55:21 +02:00

meta.zig

remove various workarounds for issues that are now fixed (#31567)

2026-03-20 19:58:33 +01:00

multi_array_list.zig

std: update for language changes

2026-03-10 10:38:50 +00:00

os.zig

std: start wrangling environment variables and process args

2026-01-04 00:27:07 -08:00

pdb.zig

compiler: various lil' fixes

2026-03-10 10:26:14 +00:00

pie.zig

std.pie: add missing clobbers on alpha and sparc

2025-11-14 12:19:38 +01:00

posix.zig

Merge pull request 'Add psp os' (#31609) from IridescentRose/zig:psp-os-target into master

2026-03-25 00:51:01 +01:00

priority_dequeue.zig

min heap is formed with less than comparison

2026-02-18 13:24:03 -08:00

priority_queue.zig

Make std.PriorityQueue an unmanaged container (#31299)

2026-02-26 21:09:52 +01:00

process.zig

windows: use enums for boolean types

2026-03-20 02:25:16 +01:00

Progress.zig

Revert "std.Progress: use cmpxchgStrong instead of cmpxchgWeak for locking/unlocking IPC"

2026-03-21 14:04:24 +01:00

Random.zig

feat(std.Random): add a linear congruent generator

2026-01-14 12:48:09 +01:00

SemanticVersion.zig

std: replace usages of std.mem.indexOf with std.mem.find

2025-12-05 14:31:27 +01:00

simd.zig

std.simd: suggest 1024-bit vectors for kvx

2025-11-10 09:40:44 +01:00

SinglyLinkedList.zig

SinglyLinkedList.remove docs: Assumes -> asserts

2025-10-25 21:28:54 -07:00

sort.zig

std.sort.partitionPoint: faster implementation (#30005)

2025-11-27 20:48:54 +01:00

start.zig

std.Target: add psp os

2026-03-21 02:56:24 -04:00

static_string_map.zig

…

std.zig

std: different mechanism for disabling network dependency

2026-03-08 19:20:34 -07:00

tar.zig

std.tar.extract: sanitize path traversal

2026-03-27 01:27:38 -07:00

Target.zig

Merge pull request 'link.MachO.Dylib: allow aarch64-macos to match arm64e-macos TBD entries' (#31673) from alexrp/zig:thanks-apple into master

2026-03-27 01:30:00 +01:00

testing.zig

checkAllAllocationFailures: provide result type to 'extra_args'

2026-03-11 02:32:29 +01:00

Thread.zig

LinuxThreadImpl: be precise in tls.prepareArea arg

2026-03-31 14:48:03 -05:00

time.zig

std: finish moving time to Io interface

2026-02-02 23:02:31 -08:00

treap.zig

std.ArrayList: make unmanaged the default

2025-08-11 15:52:49 -07:00

tz.zig

std.tz: fix redundant endian handling

2025-08-28 18:30:57 -07:00

unicode.zig

zig build fmt

2026-03-12 17:44:03 -04:00

Uri.zig

std.Uri: reject invalid URI schemes according to RFC3986

2026-03-23 05:22:46 +01:00

valgrind.zig

remove condition codes

2025-07-16 10:27:39 -07:00

wasm.zig

…

zig.zig

Merge pull request 'add an ast smith' (#31635) from gooncreeper/zig:ast-smith into master

2026-04-02 15:41:05 +02:00

zip.zig

std: rename other Dir "make" functions to "create"

2025-12-23 22:15:11 -08:00

zon.zig

zon: Add anonymous struct literal in the example

2025-08-15 23:35:16 +02:00