A safe approach to CAS and other atomic ops in Haskell.

Version on this page:0.8.3
LTS Haskell 22.26:0.8.7
Stackage Nightly 2024-06-22:0.8.8
Latest on Hackage:0.8.8

See all snapshots atomic-primops appears in

BSD-3-Clause licensed by Ryan Newton
Maintained by [email protected]
This version can be pinned in stack with:atomic-primops-0.8.3@sha256:e01558f9ee5301d0a377db41b899703d31b45afb8da37387d2f02817d46706bc,2339

Module documentation for 0.8.3

After GHC 7.4 a new casMutVar# primop became available, but it's difficult to use safely, because pointer equality is a highly unstable property in Haskell. This library provides a safer method based on the concept of Tickets.

Also, this library uses the "foreign primop" capability of GHC to add access to other variants that may be of interest, specifically, compare and swap inside an array.

Note that as of GHC 7.8, the relevant primops have been included in GHC itself. This library is engineered to work pre- and post-GHC-7.8, while exposing the same interface.


0.8.3 [2019.05.02]

  • Allow the tests to build with base-4.13 (GHC 8.8).
  • Require GHC 7.10 or later.

0.8.2 [2018.03.08]

  • Allow building with base-4.11. [2017.12.10]

  • Bundle testing/Fetch.hs with the package tarball


  • Simplify Setup.hs to support Cabal-2.0/GHC 8.2
  • Properly link store_load_barrier and friends against the GHC RTS on Windows when using GHC 8.2 or later

  • Internal changes to support forthcoming GHC 8.0


  • Implements additional fetch primops available in GHC 7.10


  • This release adds support for GHC 7.10 and its expanded library of (now inline) primops.


  • This is a good version to use for GHC 7.8.3. It includes portability and bug fixes and adds atomicModifyIORefCAS.

  • fix for GHC 7.8

  • minor ghc 7.8 fix


  • add atomicModifyIORefCAS, and bump due to prev bugfixes

  • IMPORTANT BUGFIXES - don’t use earlier versions. They have been marked deprecated.


  • Nix Data.Atomics.Counter.Foreign and the bits-atomic dependency.


  • Add advance support for GHC 7.8


  • Further internal changes, duplicate ‘cas’ routine well as barriers.
  • Add fetchAddByteArrayInt
  • Add an Unboxed counter variant that uses movable “ByteArray”s on the GHC heap.


  • Major internal change. Duplicate the barrier code from the GHC RTS and thus enable support for executables that are NOT built with ‘-threaded’.

  • Minor, add warning.


  • Add more counters


  • Critical bugfix and add Counter.

  • disable profiling

  • initial release