hadrian: Introduce ghci-wrapper package

This wraps the existing GHCi wrapper script (driver/ghci/ghci.c) in a
cabal file and adds the package to Hadrian.

2 files changed, 55 insertions, 15 deletions

diff --git a/hadrian/src/Packages.hs b/hadrian/src/Packages.hs
index fa87d8edcd..a1916b20cd 100644
--- a/hadrian/src/Packages.hs
+++ b/hadrian/src/Packages.hs
@@ -4,7 +4,7 @@ module Packages (
     array, base, binary, bytestring, cabal, checkApiAnnotations, checkPpr,
     compareSizes, compiler, containers, deepseq, deriveConstants, directory,
     exceptions, filepath, genapply, genprimopcode, ghc, ghcBignum, ghcBoot, ghcBootTh,
-    ghcCompact, ghcHeap, ghci, ghcPkg, ghcPrim, haddock, haskeline,
+    ghcCompact, ghcHeap, ghci, ghciWrapper, ghcPkg, ghcPrim, haddock, haskeline,
     hsc2hs, hp2ps, hpc, hpcBin, integerGmp, integerSimple, iserv, iservProxy,
     libffi, libiserv, mtl, parsec, pretty, primitive, process, remoteIserv, rts,
     runGhc, stm, templateHaskell, terminfo, text, time, timeout, touchy,
@@ -34,7 +34,7 @@ ghcPackages =
     [ array, base, binary, bytestring, cabal, checkPpr, checkApiAnnotations
     , compareSizes, compiler, containers, deepseq, deriveConstants, directory
     , exceptions, filepath, genapply, genprimopcode, ghc, ghcBignum, ghcBoot, ghcBootTh
-    , ghcCompact, ghcHeap, ghci, ghcPkg, ghcPrim, haddock, haskeline, hsc2hs
+    , ghcCompact, ghcHeap, ghci, ghciWrapper, ghcPkg, ghcPrim, haddock, haskeline, hsc2hs
     , hp2ps, hpc, hpcBin, integerGmp, integerSimple, iserv, libffi, libiserv, mtl
     , parsec, pretty, process, rts, runGhc, stm, templateHaskell
     , terminfo, text, time, touchy, transformers, unlit, unix, win32, xhtml
@@ -69,6 +69,8 @@ ghcBootTh           = lib  "ghc-boot-th"
 ghcCompact          = lib  "ghc-compact"
 ghcHeap             = lib  "ghc-heap"
 ghci                = lib  "ghci"
+ghciWrapper         = prg  "ghci-wrapper"    `setPath` "driver/ghci"
+                      -- See Note [Hadrian's ghci-wrapper package]
 ghcPkg              = util "ghc-pkg"
 ghcPrim             = lib  "ghc-prim"
 haddock             = util "haddock"
@@ -138,18 +140,21 @@ programName Context {..} = do
     --      use Cabal conditionals + a 'profiling' flag
     --      to declare the executable name, and I'm not sure
     --      this is allowed (or desired for that matter).
-    return $ prefix ++ case package of
-                              p | p == ghc    -> "ghc"
-                                | p == hpcBin -> "hpc"
-                                | p == iserv  -> "ghc-iserv" ++ concat [
-                                    if wayUnit' `wayUnit` way
-                                        then suffix
-                                        else ""
-                                    | (wayUnit', suffix) <- [
-                                        (Profiling, "-prof"),
-                                        (Dynamic,   "-dyn")
-                                    ]]
-                              _ -> pkgName package
+    return $ prefix ++ basename
+  where
+    basename
+      | package == ghc          = "ghc"
+      | package == ghciWrapper  = "ghci" -- See Note [Hadrian's ghci-wrapper package]
+      | package == hpcBin       = "hpc"
+      | package == iserv        = "ghc-iserv" ++ concat [
+                                        if wayUnit' `wayUnit` way
+                                            then suffix
+                                            else ""
+                                        | (wayUnit', suffix) <- [
+                                            (Profiling, "-prof"),
+                                            (Dynamic,   "-dyn")
+                                        ]]
+      | otherwise               = pkgName package
 
 -- | The 'FilePath' to a program executable in a given 'Context'.
 programPath :: Context -> Action FilePath
@@ -172,7 +177,7 @@ timeoutPath = "testsuite/timeout/install-inplace/bin/timeout" <.> exe
 -- TODO: Can we extract this information from Cabal files?
 -- | Some program packages should not be linked with Haskell main function.
 nonHsMainPackage :: Package -> Bool
-nonHsMainPackage = (`elem` [ghc, hp2ps, iserv, touchy, unlit])
+nonHsMainPackage = (`elem` [ghc, hp2ps, iserv, touchy, unlit, ghciWrapper])
 
 -- TODO: Combine this with 'programName'.
 -- | Path to the @autogen@ directory generated by 'buildAutogenFiles'.
@@ -181,6 +186,8 @@ autogenPath context@Context {..}
     | isLibrary package = autogen "build"
     | package == ghc    = autogen "build/ghc"
     | package == hpcBin = autogen "build/hpc"
+    | package == ghciWrapper = autogen "build/ghci"
+                               -- See Note [Hadrian's ghci-wrapper package]
     | otherwise         = autogen $ "build" -/- pkgName package
   where
     autogen dir = contextPath context <&> (-/- dir -/- "autogen")
@@ -218,3 +225,34 @@ libffiLibraryName = do
         (True , False) -> "ffi"
         (False, False) -> "Cffi"
         (_    , True ) -> "Cffi-6"
+
+
+{-
+Note [Hadrian's ghci-wrapper package]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+On Linux platforms the `ghci` executable is a shell-script wrapper produced
+by the binary distribution `install` rule. However, this approach is not
+viable work on Windows platforms, where binary distributions are usable
+directly after unzipping, without any need for the user to run `make install`.
+
+Moreover, Windows has rather special requirements regarding console setup and
+teardown. Consequently on Windows ghci.exe is a purpose-built executable, the
+C source of which is found in driver/ghci. Getting Hadrian to build this via
+Cabal requires a few headstands:
+
+ - Hadrian generally assumes that the name of the executable produced by a
+   'Program' package is the same as the package name. However, this is not
+   the case here: we name the package `ghci-wrapper` to avoid conflicting
+   with the `ghci` library yet we want the final executable to be named
+   `ghci.exe`. We accomplish this by overriding 'Packages.programName'.
+
+ - The executable requires a few C sources (which live in `driver/utils`) in
+   addition to the main ghci.c. Ideally these would be built independently as
+   a static library which could then be linked into the executable;
+   unfortunately Cabal doesn't support this. We instead add the sources to
+   the C-Sources list in the Cabal file.
+
+ - Unfortunately, Cabal/Hadrian's handling of C-sources appears to fall on
+   its face when a relative path is used (e.g. `../cwrapper.c`). Consequently
+   we copy the files into `driver/ghci` in the configure script.
+-}
diff --git a/hadrian/src/Settings/Default.hs b/hadrian/src/Settings/Default.hs
index d965133a88..deb9bd80b7 100644
--- a/hadrian/src/Settings/Default.hs
+++ b/hadrian/src/Settings/Default.hs
@@ -124,6 +124,8 @@ stage1Packages = do
           ++ [ libiserv | not cross ]
           ++ [ runGhc   | not cross                  ]
           ++ [ touchy   | windowsHost                ]
+             -- See Note [Hadrian's ghci-wrapper package]
+          ++ [ ghciWrapper | windowsHost             ]
           ++ [ unix     | not windowsHost            ]
           ++ [ win32    | windowsHost                ]