cabal-version: 3.8
name: ghc-stack-profiler
version: 0.2.0.0
license: BSD-3-Clause
author: Hannes Siebenhandl, Wen Kokke, Matthew Pickering
maintainer: hannes@well-typed.com
build-type: Simple
synopsis: RTS Callstack profiler for GHC.
description:
  RTS Callstack profiler for GHC.

  The main idea is to periodically sample the Haskell callstack and use IPE and [stack annotation](https://www.well-typed.com/blog/2025/09/better-haskell-stack-traces/) information in order to understand the source locations which
  correspond to the stack frames.
  To profile a program it needs to be compiled and instrumented with the 'ghc-stack-profiler' package via:

  @
  import GHC.Stack.Profiler.Sampler

  main :: IO ()
  main = 'withStackProfilerForMyThread' ('SampleIntervalMs' 10) $ do
      ...
  @

  This will spawn a profiling thread that will periodically take a snapshot of the current RTS callstack of your program and serialises it to the eventlog.

  To improve readability of the profile, compile the program with @-finfo-table-map@ and @-fdistinct-constructor-tables@.
  Using @cabal@, this can be achieved with an appropriate @cabal.project@ file:

  @
  packages: ...

  ...

  package *
      ghc-options: -finfo-table-map -fdistinct-constructor-tables
  @

  To emit the eventlog messages by the profiler, you need to run your program with the @-l@ RTS flag, for example via:

  @
  ./\<program\> ... +RTS -l -RTS
  @

  This will write out an eventlog to @\<program\>.eventlog@ which can be transformed for [speedscope.app](https://www.speedscope.app/) via the script 'ghc-stack-profiler-speedscope'.

  @
  ghc-stack-profiler-speedscope \<program\>.eventlog
  @

  The resulting profile @\<program\>.eventlog.json@ can be viewed and further analysed in [speedscope.app](https://www.speedscope.app/).

  Note that the results are affected by compilation optimisation options, such as @-fno-omit-yields@.

extra-doc-files: CHANGELOG.md
category: Profiling, Benchmarking, Development
tested-with:
  ghc ==9.10.3
  ghc ==9.12.2
  ghc ==9.14.1

common warnings
  ghc-options:
    -Wall
    -Wunused-packages

common exts
  default-extensions:
    DeriveGeneric
    DerivingStrategies
    DuplicateRecordFields
    LambdaCase
    NamedFieldPuns
    NoImportQualifiedPost
    PatternSynonyms
    ViewPatterns

  default-language: GHC2021

flag use-ghc-trace-events
  description:
    Use the package 'ghc-trace-events'. Disabling this flag makes it much easier to use @ghc-stack-profiler@ on the @ghc@ codebase, as
    we don't have to package 'ghc-trace-events' for hadrian. Always enabled on GHC <9.12.

  manual: True
  default: True

flag control
  description:
    Enable @eventlog-socket@ control commands.

  manual: True
  default: False

library
  import:
    warnings, exts

  exposed-modules:
    Debug.Trace.Binary.Compat
    GHC.Internal.ClosureTypes.Compat
    GHC.Internal.Heap.Closures.Compat
    GHC.Internal.InfoProv.Types.Compat
    GHC.Internal.Stack.Constants.Compat
    GHC.Internal.Stack.Decode.Compat
    GHC.Stack.Annotation.Experimental.Compat
    GHC.Stack.Profiler
    GHC.Stack.Profiler.Commands
    GHC.Stack.Profiler.Decode
    GHC.Stack.Profiler.FFI
    GHC.Stack.Profiler.Manager
    GHC.Stack.Profiler.Stack.Compat
    GHC.Stack.Profiler.Stack.Decode
    GHC.Stack.Profiler.SymbolTable
    GHC.Stack.Profiler.Util

  build-depends:
    async >=2.2 && <2.2.6,
    base >=4.20 && <4.23,
    binary >=0.8.9.3 && <0.11,
    bytestring >=0.11 && <0.13,
    containers >=0.6.8 && <0.9,
    ghc-heap >=9.10.1 && <9.16,
    ghc-internal >=9.1001 && <9.1600,
    ghc-stack-profiler-core ==0.2.0.0,
    stm ^>=2.5.3.0 || ^>=2.5.0.0,
    text >=2 && <2.2,

  hs-source-dirs:
    src

  if impl(ghc >=9.14)
    build-depends: ghc-experimental >=9.1400 && <9.1600

  if flag(use-ghc-trace-events) || impl(ghc <9.12)
    cpp-options:
      -DUSE_GHC_TRACE_EVENTS

    build-depends:
      ghc-trace-events ^>=0.1.2.10
  else
    build-depends:
      ghc-prim >=0.6.0 && <1

  -- Custom stack decoding for GHC <9.14.2
  -- Fixes https://github.com/well-typed/ghc-stack-profiler/issues/14
  -- See https://gitlab.haskell.org/ghc/ghc/-/issues/27009 for the fix.
  if impl(ghc <9.14.2)
    cmm-sources:
      cbits/Stack.cmm

    c-sources:
      cbits/Stack_c.c

  -- eventlog-socket custom command support
  if flag(control) && !os(windows)
    cpp-options:
      -DEVENTLOG_SOCKET_SUPPORT

    build-depends:
      eventlog-socket ^>=0.1.3

source-repository head
  type: git
  location: https://github.com/well-typed/ghc-stack-profiler.git
  subdir: ghc-stack-profiler