Use linker capability detection to improve linker use

The function `comperSupportsGhciLibs` has been renamed to
`linkerSupportsGhciLibs` because its about the linker not the compiler.

The function `comperSupportsGhciLibs` was using the compiler version
as a proxy for whether the linker supports relocatable objects. Now
support for relocatable objects is detected by running the linker.

Cabal/src/Distribution/Simple/Configure.hs

@@ -82,6 +82,7 @@ import Distribution.Simple.PackageIndex (InstalledPackageIndex)
 import qualified Distribution.Simple.PackageIndex as PackageIndex
 import Distribution.Simple.PreProcess
 import Distribution.Simple.Program
+import Distribution.Simple.Program.Db (lookupProgramByName)
 import Distribution.Simple.Setup.Common as Setup
 import Distribution.Simple.Setup.Config as Setup
 import Distribution.Simple.Utils
@@ -767,22 +768,16 @@ configure (pkg_descr0, pbi) cfg = do
  )
  return False
 
- let compilerSupportsGhciLibs :: Bool
- compilerSupportsGhciLibs =
- case compilerId comp of
- CompilerId GHC version
- | version > mkVersion [9, 3] && windows ->
- False
- CompilerId GHC _ ->
- True
- CompilerId GHCJS _ ->
- True
- _ -> False
- where
- windows = case compPlatform of
- Platform _ Windows -> True
- Platform _ _ -> False
-
+ -- Basically yes/no/unknown.
+ let linkerSupportsRelocations :: Maybe Bool
+ linkerSupportsRelocations =
+ case lookupProgramByName "ld" programDb'' of
+ Nothing -> Nothing
+ Just ld ->
+ case Map.lookup "Supports relocatable output" $ programProperties ld of
+ Just "YES" -> Just True
+ Just "NO" -> Just False
+ _other -> Nothing
  let ghciLibByDefault =
  case compilerId comp of
  CompilerId GHC _ ->
@@ -801,10 +796,12 @@ configure (pkg_descr0, pbi) cfg = do
 
  withGHCiLib_ <-
  case fromFlagOrDefault ghciLibByDefault (configGHCiLib cfg) of
- True | not compilerSupportsGhciLibs -> do
+ -- NOTE: If linkerSupportsRelocations is Nothing this may still fail if the
+ -- linker does not support -r.
+ True | not (fromMaybe True linkerSupportsRelocations) -> do
  warn verbosity $
- "--enable-library-for-ghci is no longer supported on Windows with"
- ++ " GHC 9.4 and later; ignoring..."
+ "--enable-library-for-ghci is not supported with the current"
+ ++ "  linker; ignoring..."
  return False
  v -> return v
 

Cabal/src/Distribution/Simple/Program/Db.hs

@@ -46,6 +46,7 @@ module Distribution.Simple.Program.Db
  , userSpecifyArgss
  , userSpecifiedArgs
  , lookupProgram
+ , lookupProgramByName
  , updateProgram
  , configuredPrograms
 
@@ -299,7 +300,11 @@ userSpecifiedArgs prog =
 
 -- | Try to find a configured program
 lookupProgram :: Program -> ProgramDb -> Maybe ConfiguredProgram
-lookupProgram prog = Map.lookup (programName prog) . configuredProgs
+lookupProgram = lookupProgramByName . programName
+
+-- | Try to find a configured program
+lookupProgramByName :: String -> ProgramDb -> Maybe ConfiguredProgram
+lookupProgramByName name = Map.lookup name . configuredProgs
 
 -- | Update a configured program in the database.
 updateProgram

changelog.d/pr-9443

@@ -0,0 +1,11 @@
+synopsis: Use linker capability detection to improve linker use
+packages: Cabal
+prs: #9443
+
+description: {
+
+- Previously the GHC version number and platform were used as a proxy for whether
+ the linker can generate relocatable objects.
+- Now, the ability of the linker to create relocatable objects is detected.
+
+}