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Cheng Shao pushed to branch wip/set-keep-cafs-by-need at Glasgow Haskell Compiler / GHC

Commits:

84e920db

by Cheng Shao at 2025-10-01T19:40:52+02:00

compiler: only invoke keepCAFsForGHCi if internal-interpreter is enabled

This patch makes the ghc library only invoke keepCAFsForGHCi if
internal-interpreter is enabled. For cases when it's not (e.g. the
host build of a cross ghc), this avoids unnecessarily retaining all
CAFs in the heap. Also fixes the type signature of c_keepCAFsForGHCi
to match the C ABI.

2 changed files:

compiler/GHC.hs
compiler/cbits/keepCAFsForGHCi.c

Changes:

compiler/GHC.hs

@@ -463,6 +463,9 @@ import System.Exit      ( exitWith, ExitCode(..) )
  import System.FilePath
  import System.IO.Error  ( isDoesNotExistError )
 +#if defined(HAVE_INTERNAL_INTERPRETER)
 +import Foreign.C
 +#endif
  -- %************************************************************************
  -- %*                                                                      *
@@ -597,12 +600,12 @@ withCleanupSession ghc = ghc `MC.finally` cleanup
  initGhcMonad :: GhcMonad m => Maybe FilePath -> m ()
  initGhcMonad mb_top_dir = setSession =<< liftIO ( do
 -#if !defined(javascript_HOST_ARCH)
 +#if defined(HAVE_INTERNAL_INTERPRETER)
      -- The call to c_keepCAFsForGHCi must not be optimized away. Even in non-debug builds.
      -- So we can't use assertM here.
      -- See Note [keepCAFsForGHCi] in keepCAFsForGHCi.c for details about why.
      !keep_cafs <- c_keepCAFsForGHCi
 -    massert keep_cafs
 +    massert $ keep_cafs /= 0
  #endif
      initHscEnv mb_top_dir
+   )
@@ -2092,7 +2095,7 @@ mkApiErr :: DynFlags -> SDoc -> GhcApiError
  mkApiErr dflags msg = GhcApiError (showSDoc dflags msg)
 -#if !defined(javascript_HOST_ARCH)
 +#if defined(HAVE_INTERNAL_INTERPRETER)
  foreign import ccall unsafe "keepCAFsForGHCi"
 -    c_keepCAFsForGHCi   :: IO Bool
 +    c_keepCAFsForGHCi   :: IO CBool
  #endif

compiler/cbits/keepCAFsForGHCi.c

@@ -21,7 +21,7 @@
  //   the constructor to be run, allowing the assertion to succeed in the first place
  //   as keepCAFs will have been set already during initialization of constructors.
+-
 +#if defined(HAVE_INTERNAL_INTERPRETER)
  bool keepCAFsForGHCi(void) __attribute__((constructor));
@@ -32,4 +32,4 @@ bool keepCAFsForGHCi(void)
      return was_set;
+ }
+-
 +#endif