Skip to content

GitLab

  • Projects
  • Groups
  • Snippets
  • Help
    • Loading...
  • Help
    • Help
    • Support
    • Community forum
    • Submit feedback
  • Sign in / Register
GHC
GHC
  • Project overview
    • Project overview
    • Details
    • Activity
    • Releases
  • Repository
    • Repository
    • Files
    • Commits
    • Branches
    • Tags
    • Contributors
    • Graph
    • Compare
    • Locked Files
  • Issues 4,394
    • Issues 4,394
    • List
    • Boards
    • Labels
    • Service Desk
    • Milestones
    • Iterations
  • Merge Requests 373
    • Merge Requests 373
  • Requirements
    • Requirements
    • List
  • CI / CD
    • CI / CD
    • Pipelines
    • Jobs
    • Schedules
    • Test Cases
  • Operations
    • Operations
    • Incidents
    • Environments
  • Analytics
    • Analytics
    • CI / CD
    • Code Review
    • Insights
    • Issue
    • Repository
    • Value Stream
  • Wiki
    • Wiki
  • Snippets
    • Snippets
  • Members
    • Members
  • Activity
  • Graph
  • Create a new issue
  • Jobs
  • Commits
  • Issue Boards
Collapse sidebar
  • Glasgow Haskell Compiler
  • GHCGHC
  • Issues
  • #4329

Closed
Open
Opened Sep 21, 2010 by dmbarbour@trac-dmbarbour

GHC.Conc modifyTVar primitive

I would like modifyTVar as a 'write-only' primitive supported by GHC's STM.

The semantic definition is:

modifyTVar :: TVar a -> (a -> a) -> STM () modifyTVar v f = readTVar v >>= writeTVar v . f

However, explicitly reading then writing the TVar introduces unnecessary interference between transactions. The value held by the TVar does not affect the behavior of the transaction. modifyTVar should not interfere with other transactions that only writeTVar or modifyTVar.

Even if a non-interfering implementation isn't feasible due to the underlying implementation of GHC's STM, providing the function would provide a point for a transparent upgrade in the future.

Trac metadata
Trac field Value
Version 6.12.3
Type FeatureRequest
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture
Assignee
Assign to
8.0.1
Milestone
8.0.1 (Past due)
Assign milestone
Time tracking
None
Due date
None
Reference: ghc/ghc#4329