haskell-cabal.eclass: enable dynamic linking for all binaries (ghc-7.…

…10.1_rc3)

This change will change default static linkage behaviour
from static to dynamic.

As a result linking times will speed up and binaries
will depend on more runtime haskell libraries (just like C libraries).

Binaries, like pandoc now take 500KB instead of previous 25MB blobs.

Signed-off-by: Sergei Trofimovich <siarheit@google.com>

eclass/ghc-package.eclass

@@ -126,13 +126,6 @@ ghc-supports-smp() {
 	$(ghc-getghc) --info | grep "Support SMP" | grep -q "YES"
 }
 
-# @FUNCTION: ghc-supports-dynamic-by-default
-# @DESCRIPTION:
-# checks if ghc links against shared haskell libraries by default
-ghc-supports-dynamic-by-default() {
-	$(ghc-getghc) --info | grep "Dynamic by default" | grep -q "YES"
-}
-
 # @FUNCTION: ghc-supports-interpreter
 # @DESCRIPTION:
 # checks if ghc has interpreter mode (aka GHCi)

eclass/haskell-cabal.eclass

@@ -387,8 +387,14 @@ cabal-configure() {
 
 	if $(ghc-supports-shared-libraries); then
 		# maybe a bit lower
-		if $(ghc-supports-dynamic-by-default); then
-			cabalconf+=(--enable-shared)
+		cabalconf+=(--enable-shared)
+
+		# Experimental support for dynamically linked binaries.
+		# We are enabling it since 7.10.1_rc3
+		if version_is_at_least "7.10.0.20150316" "$(ghc-version)"; then
+			# Known to break on ghc-7.8/Cabal-1.18
+			# https://ghc.haskell.org/trac/ghc/ticket/9625
+			cabalconf+=(--enable-executable-dynamic)
 		fi
 	fi