haskell-cabal.eclass: drop unused CABAL_FEATURES="alex happy c2hs cpphs"

While at it:
- dropped internal 'ghc-sanecabal()' helper
- factored out parallelism setup to new 'ghc-make-args()' function
- building initial Setup binary now also uses 'ghc-make-args()'
- dropped unused CABAL_MIN_VERSION global variable

Fixed bug in 'ghc-make-args()' to work on NOSMP ports of GHC:
We use 'qb0' to enable parallel GC. Parallel GC requires SMP
support and threaded runtime.

Reported by iota__ on arm/ghc-8 where there is support for
parallel make but not the SMP support:

    ,("Host platform","arm-unknown-linux")
    ,("Support SMP","NO")
    ,("Support parallel --make","YES")
    ,("RTS ways","l debug thr...

Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>

1 files changed, 20 insertions, 15 deletions

diff --git a/eclass/ghc-package.eclass b/eclass/ghc-package.eclass
index 5466c0b5b20d..7efa2c838449 100644
--- a/eclass/ghc-package.eclass
+++ b/eclass/ghc-package.eclass
@@ -11,7 +11,7 @@
 # @DESCRIPTION:
 # Helper eclass to handle ghc installation/upgrade/deinstallation process.
 
-inherit versionator
+inherit multiprocessing versionator
 
 # @FUNCTION: ghc-getghc
 # @DESCRIPTION:
@@ -106,20 +106,6 @@ ghc-cabal-version() {
 	fi
 }
 
-# @FUNCTION: ghc-sanecabal
-# @DESCRIPTION:
-# check if a standalone Cabal version is available for the
-# currently used ghc; takes minimal version of Cabal as
-# an optional argument
-ghc-sanecabal() {
-	local f
-	local version
-	if [[ -z "$1" ]]; then version="1.0.1"; else version="$1"; fi
-	for f in $(ghc-confdir)/cabal-*; do
-		[[ -f "${f}" ]] && version_is_at_least "${version}" "${f#*cabal-}" && return
-	done
-	return 1
-}
 # @FUNCTION: ghc-is-dynamic
 # @DESCRIPTION:
 # checks if ghc is built against dynamic libraries
@@ -193,6 +179,25 @@ ghc-libdir() {
 	echo "${_GHC_LIBDIR_CACHE}"
 }
 
+# @FUNCTION: ghc-make-args
+# @DESCRIPTION:
+# Returns default arguments passed along 'ghc --make'
+# build mode. Used mainly to enable parallel build mode.
+ghc-make-args() {
+	local ghc_make_args=()
+	# parallel on all available cores
+	if ghc-supports-smp && ghc-supports-parallel-make; then
+		# It should have been just -j$(makeopts_jobs)
+		# but GHC does not yet have nice defaults:
+		#    https://ghc.haskell.org/trac/ghc/ticket/9221#comment:57
+		# SMP is a requirement for parallel GC's gen0
+		# 'qb' balancing.
+		echo "-j$(makeopts_jobs) +RTS -A256M -qb0 -RTS"
+		ghc_make_args=()
+	fi
+	echo "${ghc_make_args[@]}"
+}
+
 # @FUNCTION: ghc-confdir
 # @DESCRIPTION:
 # returns the (Gentoo) library configuration directory, we