Fix #3041, ifndef all CURRENT_PACKAGE_KEY and related macros.

I also realized LOCAL_COMPONENT_ID is pessimal if we don't
depend on a library, so I removed it. (It has never been
in a real Cabal release.)

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Cabal/Distribution/Simple/Build/Macros.hs

@@ -37,6 +37,36 @@ import Distribution.Text
 -- * Generate cabal_macros.h
 -- ------------------------------------------------------------
 
+-- Invariant: HeaderLines always has a trailing newline
+type HeaderLines = String
+
+line :: String -> HeaderLines
+line str = str ++ "\n"
+
+ifndef :: String -> HeaderLines -> HeaderLines
+ifndef macro body =
+    line ("#ifndef " ++ macro) ++
+    body ++
+    line ("#endif /* " ++ macro ++ " */")
+
+define :: String -> Maybe [String] -> String -> HeaderLines
+define macro params val =
+    line ("#define " ++ macro ++ f params ++ " " ++ val)
+  where
+    f Nothing = ""
+    f (Just xs) = "(" ++ intercalate "," xs ++ ")"
+
+defineStr :: String -> String -> HeaderLines
+defineStr macro str = define macro Nothing (show str)
+
+ifndefDefine :: String -> Maybe [String] -> String -> HeaderLines
+ifndefDefine macro params str =
+    ifndef macro (define macro params str)
+
+ifndefDefineStr :: String -> String -> HeaderLines
+ifndefDefineStr macro str =
+    ifndef macro (defineStr macro str)
+
 -- | The contents of the @cabal_macros.h@ for the given configured package.
 --
 generate :: PackageDescription -> LocalBuildInfo -> ComponentLocalBuildInfo -> String
@@ -53,7 +83,7 @@ generate pkg_descr lbi clbi =
 --
 generatePackageVersionMacros :: [PackageIdentifier] -> String
 generatePackageVersionMacros pkgids = concat
-  [ "/* package " ++ display pkgid ++ " */\n"
+  [ line ("/* package " ++ display pkgid ++ " */")
   ++ generateMacros "" pkgname version
   | pkgid@(PackageIdentifier name version) <- pkgids
   , let pkgname = map fixchar (display name)
@@ -64,7 +94,7 @@ generatePackageVersionMacros pkgids = concat
 --
 generateToolVersionMacros :: [ConfiguredProgram] -> String
 generateToolVersionMacros progs = concat
-  [ "/* tool " ++ progid ++ " */\n"
+  [ line ("/* tool " ++ progid ++ " */")
   ++ generateMacros "TOOL_" progname version
   | prog <- progs
   , isJust . programVersion $ prog
@@ -79,29 +109,30 @@ generateToolVersionMacros progs = concat
 generateMacros :: String -> String -> Version -> String
 generateMacros macro_prefix name version =
   concat
-  ["#define ", macro_prefix, "VERSION_",name," ",show (display version),"\n"
-  ,"#define MIN_", macro_prefix, "VERSION_",name,"(major1,major2,minor) (\\\n"
-  ,"  (major1) <  ",major1," || \\\n"
-  ,"  (major1) == ",major1," && (major2) <  ",major2," || \\\n"
-  ,"  (major1) == ",major1," && (major2) == ",major2," && (minor) <= ",minor,")"
-  ,"\n\n"
-  ]
+  [ifndefDefineStr (macro_prefix ++ "VERSION_" ++ name) (display version)
+  ,ifndefDefine ("MIN_" ++ macro_prefix ++ "VERSION_" ++ name)
+                (Just ["major1","major2","minor"])
+    $ concat [
+       "(\\\n"
+      ,"  (major1) <  ",major1," || \\\n"
+      ,"  (major1) == ",major1," && (major2) <  ",major2," || \\\n"
+      ,"  (major1) == ",major1," && (major2) == ",major2," && (minor) <= ",minor,")"
+    ]
+  ,"\n"]
   where
     (major1:major2:minor:_) = map show (versionBranch version ++ repeat 0)
 
 -- | Generate the @CURRENT_COMPONENT_ID@ definition for the component ID
 --   of the current package.
 generateComponentIdMacro :: LocalBuildInfo -> ComponentLocalBuildInfo -> String
-generateComponentIdMacro lbi clbi =
+generateComponentIdMacro _lbi clbi =
   concat $
-      (case clbi of
+      [case clbi of
         LibComponentLocalBuildInfo{} ->
-          ["#define CURRENT_PACKAGE_KEY \"" ++ componentCompatPackageKey clbi ++ "\"\n"]
-        _ -> [])
-      ++
-      ["#define CURRENT_COMPONENT_ID \"" ++ display (componentComponentId clbi) ++ "\"\n"
-      ,"#define LOCAL_COMPONENT_ID \"" ++ display (localComponentId lbi) ++ "\"\n"
-      ,"\n"]
+          ifndefDefineStr "CURRENT_PACKAGE_KEY" (componentCompatPackageKey clbi)
+        _ -> ""
+      ,ifndefDefineStr "CURRENT_COMPONENT_ID" (display (componentComponentId clbi))
+      ]
 
 fixchar :: Char -> Char
 fixchar '-' = '_'

Cabal/changelog

@@ -64,6 +64,8 @@
 	* New './Setup configure' flag '--cabal-file', allowing multiple
 	.cabal files in a single directory (#3553). Primarily intended for
 	internal use.
+	* Macros in 'cabal_macros.h' are now ifndef'd, so that they
+	don't cause an error if the macro is already defined. (#3041)
 
 1.24.0.0 Ryan Thomas <ryan@ryant.org> March 2016
 	* Support GHC 8.

Cabal/tests/PackageTests/PackageTester.hs

@@ -101,10 +101,8 @@ import Distribution.Simple.Configure
 import Distribution.Verbosity (Verbosity)
 import Distribution.Simple.BuildPaths (exeExtension)
 
-#ifndef LOCAL_COMPONENT_ID
 import Distribution.Simple.Utils (cabalVersion)
 import Distribution.Text (display)
-#endif
 
 import qualified Test.Tasty.HUnit as HUnit
 import Text.Regex.Posix
@@ -389,10 +387,6 @@ cabal' cmd extraArgs0 = do
                 -- Cabal is going to configure it and usually figure
                 -- out the right location in any case.
                 -- , "--with-ghc-pkg", withGhcPkgPath suite
-                -- Would really like to do this, but we're not always
-                -- going to be building against sufficiently recent
-                -- Cabal which provides this macro.
-                -- , "--dependency=Cabal=" ++ LOCAL_COMPONENT_ID
                 -- These flags make the test suite run faster
                 -- Can't do this unless we LD_LIBRARY_PATH correctly
                 -- , "--enable-executable-dynamic"
@@ -469,11 +463,6 @@ rawCompileSetup verbosity suite e path = do
         [ "--make"] ++
         ghcPackageDBParams (ghcVersion suite) (packageDBStack suite) ++
         [ "-hide-package Cabal"
-#ifdef LOCAL_COMPONENT_ID
-        -- This is best, but we don't necessarily have it
-        -- if we're bootstrapping with old Cabal.
-        , "-package-id " ++ LOCAL_COMPONENT_ID
-#else
         -- This mostly works, UNLESS you've installed a
         -- version of Cabal with the SAME version number.
         -- Then old GHCs will incorrectly select the installed
@@ -482,7 +471,6 @@ rawCompileSetup verbosity suite e path = do
         -- at all, except if there's a later version of Cabal
         -- installed GHC will prefer that.
         , "-package Cabal-" ++ display cabalVersion
-#endif
         , "-O0"
         , "Setup.hs" ]
     unless (resultExitCode r == ExitSuccess) $