Fix GhcThreaded settingwip/T17692

This adopts a patch from NetBSD's packaging fixing the `GhcThreaded`
option of the make build system. In addition we introduce a `ghcThreaded`
option in hadrian's `Flavour` type.

Also fix Hadrian's treatment of the `Use Threaded` entry in `settings`.
Previously it would incorrectly claim `Use Threaded = True` if we were
building the `threaded` runtime way. However, this is inconsistent with
the `make` build system, which defines it to be whether the `ghc`
executable is linked against the threaded runtime.

Fixes #17692.

6 files changed, 15 insertions, 2 deletions

diff --git a/ghc/ghc.mk b/ghc/ghc.mk
index 3bff2f58c9..8c112a054f 100644
--- a/ghc/ghc.mk
+++ b/ghc/ghc.mk
@@ -61,7 +61,13 @@ ifeq "$(GhcThreaded)" "YES"
 # Use threaded RTS with GHCi, so threads don't get blocked at the prompt.
 ghc_stage2_MORE_HC_OPTS += -threaded
 ghc_stage3_MORE_HC_OPTS += -threaded
+else
+# Opt out from threaded GHC. See ghc-bin.cabal.in
+ghc_stage2_CONFIGURE_OPTS += -f-threaded
+ghc_stage3_CONFIGURE_OPTS += -f-threaded
 endif
+# Stage-0 compiler isn't guaranteed to have a threaded RTS.
+ghc_stage1_CONFIGURE_OPTS += -f-threaded
 
 ifeq "$(GhcProfiled)" "YES"
 ghc_stage2_PROGRAM_WAY = p
diff --git a/hadrian/doc/user-settings.md b/hadrian/doc/user-settings.md
index 04a526605d..02b6ddf9ea 100644
--- a/hadrian/doc/user-settings.md
+++ b/hadrian/doc/user-settings.md
@@ -35,6 +35,8 @@ data Flavour = Flavour {
     ghcProfiled :: Bool,
     -- | Build GHC with debug information.
     ghcDebugged :: Bool
+    -- | Build the GHC executable against the threaded runtime system.
+    ghcThreaded :: Bool,
     -- | Whether to build docs and which ones
     --   (haddocks, user manual, haddock manual)
     ghcDocs :: Action DocTargets }
diff --git a/hadrian/src/Flavour.hs b/hadrian/src/Flavour.hs
index dd203ea88e..64ce931e78 100644
--- a/hadrian/src/Flavour.hs
+++ b/hadrian/src/Flavour.hs
@@ -39,6 +39,8 @@ data Flavour = Flavour {
     ghcProfiled :: Bool,
     -- | Build GHC with debugging assertions.
     ghcDebugged :: Bool,
+    -- | Build the GHC executable against the threaded runtime system.
+    ghcThreaded :: Bool,
     -- | Whether to build docs and which ones
     --   (haddocks, user manual, haddock manual)
     ghcDocs :: Action DocTargets }
diff --git a/hadrian/src/Rules/Generate.hs b/hadrian/src/Rules/Generate.hs
index 74759be20e..c65d852931 100644
--- a/hadrian/src/Rules/Generate.hs
+++ b/hadrian/src/Rules/Generate.hs
@@ -320,7 +320,7 @@ generateSettings = do
         , ("Tables next to code", expr $ yesNo <$> flag TablesNextToCode)
         , ("Leading underscore", expr $ yesNo <$> flag LeadingUnderscore)
         , ("Use LibFFI", expr $ yesNo <$> useLibFFIForAdjustors)
-        , ("Use Threads", yesNo . any (wayUnit Threaded) <$> getRtsWays)
+        , ("Use Threads", expr $ yesNo . ghcThreaded <$> flavour)
         , ("Use Debugging", expr $ yesNo . ghcDebugged <$> flavour)
         , ("RTS expects libdw", yesNo <$> getFlag WithLibdw)
         ]
diff --git a/hadrian/src/Settings/Default.hs b/hadrian/src/Settings/Default.hs
index 7279023e82..5bf9ea7e7c 100644
--- a/hadrian/src/Settings/Default.hs
+++ b/hadrian/src/Settings/Default.hs
@@ -215,6 +215,7 @@ defaultFlavour = Flavour
     , ghciWithDebugger   = False
     , ghcProfiled        = False
     , ghcDebugged        = False
+    , ghcThreaded        = True
     , ghcDocs            = cmdDocsArgs }
 
 -- | Default logic for determining whether to build
diff --git a/hadrian/src/Settings/Packages.hs b/hadrian/src/Settings/Packages.hs
index 9e43459a0f..d0dbabde99 100644
--- a/hadrian/src/Settings/Packages.hs
+++ b/hadrian/src/Settings/Packages.hs
@@ -96,7 +96,9 @@ packageArgs = do
             -- the 'threaded' flag is True by default, but
             -- let's record explicitly that we link all ghc
             -- executables with the threaded runtime.
-            , arg "threaded" ] ]
+            , stage0 ? arg "-threaded"
+            , notStage0 ? ifM (ghcThreaded <$> expr flavour) (arg "threaded") (arg "-threaded") ]
+          ]
 
         -------------------------------- ghcPkg --------------------------------
         , package ghcPkg ?