From 235474e7ae582d66081d8e44666beb2f7638fdd3 Mon Sep 17 00:00:00 2001
From: Matthew Pickering <matthewtpickering@gmail.com>
Date: Mon, 9 May 2022 18:23:15 +0100
Subject: hadrian: Only copy and install libffi headers when using in-tree
 libffi

When passed `--use-system-libffi` then we shouldn't copy and install the
headers from the system package. Instead the headers are expected to be
available as a runtime dependency on the users system.

Fixes #21485 #21487
---
 hadrian/src/Rules/Generate.hs | 4 +++-
 hadrian/src/Rules/Rts.hs      | 2 +-
 rts/rts.cabal.in              | 6 +++---
 3 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/hadrian/src/Rules/Generate.hs b/hadrian/src/Rules/Generate.hs
index aaa83e0060..5653bd1d25 100644
--- a/hadrian/src/Rules/Generate.hs
+++ b/hadrian/src/Rules/Generate.hs
@@ -41,13 +41,15 @@ rtsDependencies :: Expr [FilePath]
 rtsDependencies = do
     stage   <- getStage
     rtsPath <- expr (rtsBuildPath stage)
+    useSystemFfi <- expr (flag UseSystemFfi)
+
     let headers =
             [ "ghcautoconf.h", "ghcplatform.h"
             , "DerivedConstants.h"
             , "rts" -/- "EventTypes.h"
             , "rts" -/- "EventLogConstants.h"
             ]
-            ++ libffiHeaderFiles
+            ++ (if useSystemFfi then [] else libffiHeaderFiles)
     pure $ ((rtsPath -/- "include") -/-) <$> headers
 
 genapplyDependencies :: Expr [FilePath]
diff --git a/hadrian/src/Rules/Rts.hs b/hadrian/src/Rules/Rts.hs
index 59a337801f..9a18a41c46 100644
--- a/hadrian/src/Rules/Rts.hs
+++ b/hadrian/src/Rules/Rts.hs
@@ -126,7 +126,7 @@ needRtsLibffiTargets stage = do
     let headers = fmap ((rtsPath -/- "include") -/-) libffiHeaderFiles
 
     if useSystemFfi
-    then return headers
+    then return []
     else do
         -- Need Libffi
         -- This returns the dynamic library files (in the Libffi build dir).
diff --git a/rts/rts.cabal.in b/rts/rts.cabal.in
index ff60f1b456..cc449ee522 100644
--- a/rts/rts.cabal.in
+++ b/rts/rts.cabal.in
@@ -73,6 +73,9 @@ library
         extra-bundled-libraries: Cffi-6
       else
         extra-bundled-libraries: Cffi
+      install-includes: ffi.h ffitarget.h
+      -- ^ see Note [Packaging libffi headers] in
+      -- GHC.Driver.CodeOutput.
 
     -- The make build system does something special in config.mk.in
     -- for generating profiled, debugged, etc builds of those
@@ -160,9 +163,6 @@ library
                       ghcautoconf.h ghcconfig.h ghcplatform.h ghcversion.h
                       -- ^ from include
                       DerivedConstants.h
-                      ffi.h ffitarget.h
-                      -- ^ see Note [Packaging libffi headers] in
-                      -- GHC.Driver.CodeOutput.
                       rts/EventLogConstants.h
                       rts/EventTypes.h
                       -- ^ generated
-- 
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