From 82bc91a548ad91241f42cefc528c5d5bffed2f5a Mon Sep 17 00:00:00 2001
From: Peter Simons <simons@cryp.to>
Date: Sat, 19 Oct 2013 13:48:33 +0200
Subject: [PATCH] build-support/cabal: add an option to enable shared library
 support

enableSharedLibraries configures Cabal to build of shared libraries. This
option requires that all dependencies of the package have been compiled
for use in shared libraries, too.

enableSharedExecutables configures Cabal to prefer shared libraries when
linking executables.

This patch partly fixes issue #1084.
---
 pkgs/build-support/cabal/default.nix | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/pkgs/build-support/cabal/default.nix b/pkgs/build-support/cabal/default.nix
index a1dc68e6484..6794a7a4be1 100644
--- a/pkgs/build-support/cabal/default.nix
+++ b/pkgs/build-support/cabal/default.nix
@@ -2,6 +2,8 @@
 
 { stdenv, fetchurl, lib, pkgconfig, ghc, Cabal, jailbreakCabal, glibcLocales
 , enableLibraryProfiling ? false
+, enableSharedLibraries ? false
+, enableSharedExecutables ? false
 , enableCheckPhase ? true
 }:
 
@@ -42,8 +44,12 @@ assert enableCheckPhase -> stdenv.lib.versionOlder "7" ghc.ghcVersion;
             # if that is not desired (for applications), name can be set to
             # fname.
             name = if self.isLibrary then
-                     if enableLibraryProfiling then
+                     if enableLibraryProfiling && self.enableSharedLibraries then
+                       "haskell-${self.pname}-ghc${ghc.ghc.version}-${self.version}-profiling-shared"
+                     else if enableLibraryProfiling && !self.enableSharedLibraries then
                        "haskell-${self.pname}-ghc${ghc.ghc.version}-${self.version}-profiling"
+                     else if !enableLibraryProfiling && self.enableSharedLibraries then
+                       "haskell-${self.pname}-ghc${ghc.ghc.version}-${self.version}-shared"
                      else
                        "haskell-${self.pname}-ghc${ghc.ghc.version}-${self.version}"
                    else
@@ -107,8 +113,18 @@ assert enableCheckPhase -> stdenv.lib.versionOlder "7" ghc.ghcVersion;
             # and run any regression test suites the package might have
             doCheck = enableCheckPhase;
 
+            # pass the '--enable-shared' flag to cabal in the configure
+            # stage to enable building shared libraries
+            inherit enableSharedLibraries;
+
+            # pass the '--enable-executable-dynamic' flag to cabal in
+            # the configure stage to enable linking shared libraries
+            inherit enableSharedExecutables;
+
             extraConfigureFlags = [
               (stdenv.lib.enableFeature enableLibraryProfiling "library-profiling")
+              (stdenv.lib.enableFeature self.enableSharedLibraries "shared")
+              (stdenv.lib.enableFeature self.enableSharedExecutables "executable-dynamic")
               (stdenv.lib.enableFeature self.enableSplitObjs "split-objs")
             ] ++ stdenv.lib.optional (stdenv.lib.versionOlder "7" ghc.ghcVersion) (stdenv.lib.enableFeature self.doCheck "tests");