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Ben Gamari pushed to branch ghc-9.14 at Glasgow Haskell Compiler / GHC

Commits:

02150b65

by Alison at 2025-10-28T15:02:30-04:00

ghc-heap: Fix race condition with profiling builds

Apply the same fix from Closures.hs (64fd0fac83) to Heap.hs by adding
empty imports to make way-dependent dependencies visible to `ghc -M`.

Fixes #15197, #26407

(cherry picked from commit 99b233f45064ec8a10df28cd53ed70ce62e85a1e)

1 changed file:

libraries/ghc-heap/GHC/Exts/Heap.hs

Changes:

libraries/ghc-heap/GHC/Exts/Heap.hs

@@ -67,10 +67,26 @@ import GHC.Exts.Heap.ClosureTypes
  import GHC.Exts.Heap.Constants
  import GHC.Exts.Heap.ProfInfo.Types
  #if defined(PROFILING)
 +import GHC.Exts.Heap.InfoTable () -- See Note [No way-dependent imports]
  import GHC.Exts.Heap.InfoTableProf
  #else
  import GHC.Exts.Heap.InfoTable
 +import GHC.Exts.Heap.InfoTableProf () -- See Note [No way-dependent imports]
++
 +{-
 +Note [No way-dependent imports]
 +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 +`ghc -M` currently assumes that the imports for a module are the same
 +in every way.  This is arguably a bug, but breaking this assumption by
 +importing different things in different ways can cause trouble.  For
 +example, this module in the profiling way imports and uses
 +GHC.Exts.Heap.InfoTableProf.  When it was not also imported in the
 +vanilla way, there were intermittent build failures due to this module
 +being compiled in the profiling way before GHC.Exts.Heap.InfoTableProf
 +in the profiling way. (#15197)
 +-}
  #endif
++
  import GHC.Exts.Heap.Utils
  import qualified GHC.Exts.Heap.FFIClosures as FFIClosures
  import qualified GHC.Exts.Heap.ProfInfo.PeekProfInfo as PPI