Generate `ghcversion.h` from a `.in` file

Now that there are no conditional sections (see the previous commit), we
can just a do simple substitution rather than pasting it together line
by line.

Progress on #23966

configure.ac

@@ -68,21 +68,6 @@ FP_PROG_SORT
 dnl ----------------------------------------------------------
 FP_SETUP_PROJECT_VERSION
 
-dnl Don't use AC_DEFINE because it will make C-style comments invalid for
-dnl Haskell.
-
-> rts/include/ghcversion.h
-
-cat rts/ghcversion.h.top                                                >> rts/include/ghcversion.h
-
-echo "#define __GLASGOW_HASKELL__ ${ProjectVersionInt}"                 >> rts/include/ghcversion.h
-echo "#define __GLASGOW_HASKELL_FULL_VERSION__ \"${ProjectVersion}\""   >> rts/include/ghcversion.h
-echo                                                                    >> rts/include/ghcversion.h
-echo "#define __GLASGOW_HASKELL_PATCHLEVEL1__ ${ProjectPatchLevel1}"    >> rts/include/ghcversion.h
-echo "#define __GLASGOW_HASKELL_PATCHLEVEL2__ ${ProjectPatchLevel2}"    >> rts/include/ghcversion.h
-
-cat rts/ghcversion.h.bottom                                             >> rts/include/ghcversion.h
-
 # Hmmm, we fix the RPM release number to 1 here... Is this convenient?
 AC_SUBST([release], [1])
 
@@ -103,8 +88,6 @@ AC_PREREQ([2.69])
 AC_CONFIG_HEADER(mk/config.h)
 # This one is manually maintained.
 AC_CONFIG_HEADER(compiler/ghc-llvm-version.h)
-dnl manually outputted above, for reasons described there.
-dnl AC_CONFIG_HEADER(rts/include/ghcversion.h)
 
 # No, semi-sadly, we don't do `--srcdir'...
 if test x"$srcdir" != 'x.' ; then

hadrian/src/Rules/Generate.hs

@@ -323,6 +323,12 @@ templateRules = do
   templateRule "utils/ghc-pkg/ghc-pkg.cabal" $ projectVersion
   templateRule "libraries/template-haskell/template-haskell.cabal" $ projectVersion
   templateRule "libraries/prologue.txt" $ packageVersions
+  templateRule "rts/include/ghcversion.h" $ mconcat
+    [ interpolateSetting "ProjectVersionInt" ProjectVersionInt
+    , interpolateSetting "ProjectVersion" ProjectVersion
+    , interpolateSetting "ProjectPatchLevel1" ProjectPatchLevel1
+    , interpolateSetting "ProjectPatchLevel2" ProjectPatchLevel2
+    ]
   templateRule "docs/index.html" $ packageVersions
   templateRule "docs/users_guide/ghc_config.py" $ mconcat
     [ projectVersion

hadrian/src/Settings/Builders/Cabal.hs

@@ -166,9 +166,14 @@ configureStageArgs = do
   let cFlags  = getStagedCCFlags
       linkFlags = prgFlags . ccLinkProgram . tgtCCompilerLink <$> getStagedTarget
   mconcat [ configureArgs cFlags linkFlags
-          , notStage0 ? arg "--ghc-option=-ghcversion-file=rts/include/ghcversion.h"
+          , ghcVersionH
           ]
 
+ghcVersionH :: Args
+ghcVersionH = notStage0 ? do
+    let h = "rts/include/ghcversion.h"
+    expr $ need [h]
+    arg $ "--ghc-option=-ghcversion-file=" <> h
 
 configureArgs :: Args -> Args -> Args
 configureArgs cFlags' ldFlags' = do
@@ -199,7 +204,7 @@ configureArgs cFlags' ldFlags' = do
         -- ROMES:TODO: how is the Host set to TargetPlatformFull? That would be the target
         , conf "--host"                   $ arg =<< getSetting TargetPlatformFull
         , conf "--with-cc" $ arg =<< getBuilderPath . (Cc CompileC) =<< getStage
-        , notStage0 ? arg "--ghc-option=-ghcversion-file=rts/include/ghcversion.h"
+        , ghcVersionH
         ]
 
 bootPackageConstraints :: Args

rts/ghcversion.h.top

-#if !defined(__GHCVERSION_H__)
-#define __GHCVERSION_H__
-

rts/ghcversion.h.bottom → rts/include/ghcversion.h.in

+#if !defined(__GHCVERSION_H__)
+#define __GHCVERSION_H__
+
+#define __GLASGOW_HASKELL__ @ProjectVersionInt@
+#define __GLASGOW_HASKELL_FULL_VERSION__ "@ProjectVersion@"
+
+#define __GLASGOW_HASKELL_PATCHLEVEL1__ @ProjectPatchLevel1@
+#define __GLASGOW_HASKELL_PATCHLEVEL2__ @ProjectPatchLevel2@
 
 #define MIN_VERSION_GLASGOW_HASKELL(ma,mi,pl1,pl2) ( \
    ((ma)*100+(mi)) <  __GLASGOW_HASKELL__ || \