Include CPP preprocessor dependencies in -M output

Issue #16521

10 files changed, 102 insertions, 1 deletions

diff --git a/compiler/main/DriverMkDepend.hs b/compiler/main/DriverMkDepend.hs
index 741104596a..6368d8c785 100644
--- a/compiler/main/DriverMkDepend.hs
+++ b/compiler/main/DriverMkDepend.hs
@@ -41,6 +41,7 @@ import System.IO
 import System.IO.Error  ( isEOFError )
 import Control.Monad    ( when )
 import Data.Maybe       ( isJust )
+import Data.IORef
 
 -----------------------------------------------------------------
 --
@@ -85,7 +86,7 @@ doMkDependHS srcs = do
     -- Print out the dependencies if wanted
     liftIO $ debugTraceMsg dflags 2 (text "Module dependencies" $$ ppr sorted)
 
-    -- Prcess them one by one, dumping results into makefile
+    -- Process them one by one, dumping results into makefile
     -- and complaining about cycles
     hsc_env <- getSession
     root <- liftIO getCurrentDirectory
@@ -224,6 +225,18 @@ processDeps dflags hsc_env excl_mods root hdl (AcyclicSCC node)
                 -- Something like       A.o : A.hs
         ; writeDependency root hdl obj_files src_file
 
+                -- Emit a dependency for each CPP import
+        ; when (depIncludeCppDeps dflags) $ do
+            -- CPP deps are descovered in the module parsing phase by parsing
+            -- comment lines left by the preprocessor.
+            -- Note that GHC.parseModule may throw an exception if the module
+            -- fails to parse, which may not be desirable (see #16616).
+          { session <- Session <$> newIORef hsc_env
+          ; parsedMod <- reflectGhc (GHC.parseModule node) session
+          ; mapM_ (writeDependency root hdl obj_files)
+                  (GHC.pm_extra_src_files parsedMod)
+          }
+
                 -- Emit a dependency for each import
 
         ; let do_imps is_boot idecls = sequence_
diff --git a/compiler/main/DynFlags.hs b/compiler/main/DynFlags.hs
index e94798aede..15f254ad7c 100644
--- a/compiler/main/DynFlags.hs
+++ b/compiler/main/DynFlags.hs
@@ -1022,6 +1022,7 @@ data DynFlags = DynFlags {
   --  For ghc -M
   depMakefile           :: FilePath,
   depIncludePkgDeps     :: Bool,
+  depIncludeCppDeps     :: Bool,
   depExcludeMods        :: [ModuleName],
   depSuffixes           :: [String],
 
@@ -2010,6 +2011,7 @@ defaultDynFlags mySettings (myLlvmTargets, myLlvmPasses) =
         -- ghc -M values
         depMakefile       = "Makefile",
         depIncludePkgDeps = False,
+        depIncludeCppDeps = False,
         depExcludeMods    = [],
         depSuffixes       = [],
         -- end of ghc -M values
@@ -2684,6 +2686,9 @@ addOptP   f = alterSettings (\s -> s { sOpt_P   = f : sOpt_P s
 setDepMakefile :: FilePath -> DynFlags -> DynFlags
 setDepMakefile f d = d { depMakefile = f }
 
+setDepIncludeCppDeps :: Bool -> DynFlags -> DynFlags
+setDepIncludeCppDeps b d = d { depIncludeCppDeps = b }
+
 setDepIncludePkgDeps :: Bool -> DynFlags -> DynFlags
 setDepIncludePkgDeps b d = d { depIncludePkgDeps = b }
 
@@ -3100,6 +3105,8 @@ dynamic_flags_deps = [
         -------- ghc -M -----------------------------------------------------
   , make_ord_flag defGhcFlag "dep-suffix"              (hasArg addDepSuffix)
   , make_ord_flag defGhcFlag "dep-makefile"            (hasArg setDepMakefile)
+  , make_ord_flag defGhcFlag "include-cpp-deps"
+        (noArg (setDepIncludeCppDeps True))
   , make_ord_flag defGhcFlag "include-pkg-deps"
         (noArg (setDepIncludePkgDeps True))
   , make_ord_flag defGhcFlag "exclude-module"          (hasArg addDepExcludeMod)
diff --git a/docs/users_guide/separate_compilation.rst b/docs/users_guide/separate_compilation.rst
index d591736ed4..c8a816ccd1 100644
--- a/docs/users_guide/separate_compilation.rst
+++ b/docs/users_guide/separate_compilation.rst
@@ -1425,6 +1425,20 @@ generation are:
     imported by the home package module. This option is normally only
     used by the various system libraries.
 
+.. ghc-flag:: -include-cpp-deps
+    :shortdesc: Include preprocessor dependencies
+    :type: dynamic
+    :category:
+
+    Output preprocessor dependencies. This only has an effect when the CPP
+    language extension is enabled. These dependencies are files included with
+    the ``#include`` preprocessor directive (as well as transitive includes) and
+    implicitly included files such as standard c preprocessor headers and a GHC
+    version header. One exception to this is that GHC generates a temporary
+    header file (during compilation) containing package version macros. As this
+    is only a temporary file that GHC will always generate, it is not output as
+    a dependency.
+
 .. _orphan-modules:
 
 Orphan modules and instance declarations
diff --git a/testsuite/tests/driver/T16521/A.hs b/testsuite/tests/driver/T16521/A.hs
new file mode 100644
index 0000000000..ddcfdbcf41
--- /dev/null
+++ b/testsuite/tests/driver/T16521/A.hs
@@ -0,0 +1,14 @@
+{-# LANGUAGE CPP #-}
+
+module A where
+
+#include "a.h"
+#include "b.h"
+
+-- Test including a header from an external package.
+#include "processFlags.h"
+
+main :: IO ()
+main = do
+    putStrLn a
+    putStrLn b
\ No newline at end of file
diff --git a/testsuite/tests/driver/T16521/Makefile b/testsuite/tests/driver/T16521/Makefile
new file mode 100644
index 0000000000..4b3fb94742
--- /dev/null
+++ b/testsuite/tests/driver/T16521/Makefile
@@ -0,0 +1,9 @@
+TOP=../../..
+include $(TOP)/mk/boilerplate.mk
+include $(TOP)/mk/test.mk
+
+T16521 :
+	rm -f Makefile.out
+	'$(TEST_HC)' $(TEST_HC_OPTS) -package process -M -include-cpp-deps -dep-suffix "" -dep-makefile Makefile1.out A.hs 2>&1 > /dev/null
+	'$(TEST_HC)' $(TEST_HC_OPTS) -package process -M -include-cpp-deps -dep-suffix "" -dep-suffix "_" -dep-makefile Makefile2.out A.hs 2>&1 > /dev/null
+	./check.sh
\ No newline at end of file
diff --git a/testsuite/tests/driver/T16521/a.h b/testsuite/tests/driver/T16521/a.h
new file mode 100644
index 0000000000..1fc4634db4
--- /dev/null
+++ b/testsuite/tests/driver/T16521/a.h
@@ -0,0 +1 @@
+a = "a"
\ No newline at end of file
diff --git a/testsuite/tests/driver/T16521/all.T b/testsuite/tests/driver/T16521/all.T
new file mode 100644
index 0000000000..e00a23262f
--- /dev/null
+++ b/testsuite/tests/driver/T16521/all.T
@@ -0,0 +1,7 @@
+test('T16521', extra_files( \
+    [ 'A.hs' \
+    , 'a.h' \
+    , 'b.h' \
+    , 'b2.h' \
+    , 'check.sh'
+    ]), makefile_test, [])
diff --git a/testsuite/tests/driver/T16521/b.h b/testsuite/tests/driver/T16521/b.h
new file mode 100644
index 0000000000..a6d6eaf067
--- /dev/null
+++ b/testsuite/tests/driver/T16521/b.h
@@ -0,0 +1,2 @@
+#include "b2.h"
+b = "b" ++ b2
\ No newline at end of file
diff --git a/testsuite/tests/driver/T16521/b2.h b/testsuite/tests/driver/T16521/b2.h
new file mode 100644
index 0000000000..cbbc1af9e7
--- /dev/null
+++ b/testsuite/tests/driver/T16521/b2.h
@@ -0,0 +1 @@
+b2 = "bb"
\ No newline at end of file
diff --git a/testsuite/tests/driver/T16521/check.sh b/testsuite/tests/driver/T16521/check.sh
new file mode 100755
index 0000000000..1fbecd6231
--- /dev/null
+++ b/testsuite/tests/driver/T16521/check.sh
@@ -0,0 +1,33 @@
+#! /bin/sh
+
+checkDups() {
+	# Check for duplicate lines
+	if [ $(uniq $1 -d | wc -l) -ne 0 ]
+	then
+		echo "Duplicate dependencies:"
+		uniq $1 -d
+	fi
+}
+
+expectDep() {
+	if ! grep -q $1 "$2" $3
+	then
+		echo "Missing: \"$2\""
+	fi
+}
+
+checkDups Makefile1.out
+expectDep -F "A.o : A.hs" Makefile1.out
+expectDep -F "A.o : a.h" Makefile1.out
+expectDep -F "A.o : b.h" Makefile1.out
+expectDep -F "A.o : b2.h" Makefile1.out
+expectDep "" "A\.o : .*/ghcversion.h" Makefile1.out
+expectDep "" "A\.o : .*/processFlags.h" Makefile1.out
+
+checkDups Makefile2.out
+expectDep -F "A._o A.o : A.hs" Makefile2.out
+expectDep -F "A._o A.o : a.h" Makefile2.out
+expectDep -F "A._o A.o : b.h" Makefile2.out
+expectDep -F "A._o A.o : b2.h" Makefile2.out
+expectDep "" "A\._o A\.o : .*/ghcversion.h" Makefile2.out
+expectDep "" "A\._o A\.o : .*/processFlags.h" Makefile2.out
\ No newline at end of file