diff --git a/pkgs/development/interpreters/ruby/ruby-1.8.7.nix b/pkgs/development/interpreters/ruby/ruby-1.8.7.nix
index 3c2ea71ecf2..0ae1d1261ee 100644
--- a/pkgs/development/interpreters/ruby/ruby-1.8.7.nix
+++ b/pkgs/development/interpreters/ruby/ruby-1.8.7.nix
@@ -60,6 +60,9 @@ stdenv.mkDerivation rec {
   ];
 
   configureFlags = [ "--enable-shared" "--enable-pthread" ]
+    # Without this fails due to not finding X11/Xlib.h
+    # Not sure why this isn't required on Linux
+    ++ ops stdenv.isDarwin [ "--without-tcl" "--without-tk" ]
     ++ op useRailsExpress "--with-baseruby=${baseruby}/bin/ruby";
 
   installFlags = stdenv.lib.optionalString docSupport "install-doc";
diff --git a/pkgs/development/libraries/botan/generic.nix b/pkgs/development/libraries/botan/generic.nix
index c843a00b836..5880ae772ce 100644
--- a/pkgs/development/libraries/botan/generic.nix
+++ b/pkgs/development/libraries/botan/generic.nix
@@ -21,7 +21,7 @@ stdenv.mkDerivation rec {
   buildInputs = [ python bzip2 zlib gmp openssl boost ];
 
   configurePhase = ''
-    python configure.py --prefix=$out --with-bzip2 --with-zlib ${if openssl != null then "--with-openssl" else ""} ${extraConfigureFlags}
+    python configure.py --prefix=$out --with-bzip2 --with-zlib ${if openssl != null then "--with-openssl" else ""} ${extraConfigureFlags}${if stdenv.cc.isClang then " --cc=clang" else "" }
   '';
 
   enableParallelBuilding = true;
diff --git a/pkgs/development/libraries/libdvbpsi/default.nix b/pkgs/development/libraries/libdvbpsi/default.nix
index 6af8e7a415e..f8b9e9ecef9 100644
--- a/pkgs/development/libraries/libdvbpsi/default.nix
+++ b/pkgs/development/libraries/libdvbpsi/default.nix
@@ -12,7 +12,7 @@ stdenv.mkDerivation {
   meta = {
     description = "A simple library designed for decoding and generation of MPEG TS and DVB PSI tables according to standards ISO/IEC 13818 and ITU-T H.222.0";
     homepage = http://www.videolan.org/developers/libdvbpsi.html ;
-    platforms = stdenv.lib.platforms.linux;
+    platforms = stdenv.lib.platforms.unix;
     license = stdenv.lib.licenses.lgpl21;
   };
 
diff --git a/pkgs/development/libraries/libev/default.nix b/pkgs/development/libraries/libev/default.nix
index 90cab2cc687..ce7d7b9e275 100644
--- a/pkgs/development/libraries/libev/default.nix
+++ b/pkgs/development/libraries/libev/default.nix
@@ -7,6 +7,11 @@ stdenv.mkDerivation rec {
     url = "http://dist.schmorp.de/libev/${name}.tar.gz";
     sha256 = "1jyw7qbl0spxqa0dccj9x1jsw7cj7szff43cq4acmklnra4mzz48";
   };
+
+  # Version 4.19 is not valid C11 (which Clang default to)
+  # Check if this is still necessary on upgrade
+  NIX_CFLAGS_COMPILE = if stdenv.cc.isClang then "-std=c99" else null;
+
   meta = {
     description = "A high-performance event loop/event model with lots of features";
     maintainers = [ stdenv.lib.maintainers.raskin ];
diff --git a/pkgs/development/libraries/nghttp2/default.nix b/pkgs/development/libraries/nghttp2/default.nix
index e442cc96d2f..bc8c599a901 100644
--- a/pkgs/development/libraries/nghttp2/default.nix
+++ b/pkgs/development/libraries/nghttp2/default.nix
@@ -42,6 +42,12 @@ stdenv.mkDerivation rec {
     sha256 = "000d50yzyysbr9ldhvnbpzn35vplqm08dnmh55wc5zk273gy383f";
   };
 
+  # Configure script searches for a symbol which does not exist in jemalloc on Darwin
+  # Reported upstream in https://github.com/tatsuhiro-t/nghttp2/issues/233
+  postPatch = if (stdenv.isDarwin && optJemalloc != null) then ''
+    substituteInPlace configure --replace "malloc_stats_print" "je_malloc_stats_print"
+  '' else null;
+
   nativeBuildInputs = [ pkgconfig ];
   buildInputs = [ optJansson optBoost optLibxml2 optJemalloc ]
     ++ stdenv.lib.optionals hasApp [ optOpenssl optLibev optZlib ];
diff --git a/pkgs/tools/misc/bandwidth/default.nix b/pkgs/tools/misc/bandwidth/default.nix
index 35b13448b59..ff5e47336d3 100644
--- a/pkgs/tools/misc/bandwidth/default.nix
+++ b/pkgs/tools/misc/bandwidth/default.nix
@@ -19,7 +19,8 @@ stdenv.mkDerivation rec {
 
   buildInputs = [ nasm ];
 
-  buildFlags = [ arch ];
+  buildFlags = [ arch ]
+    ++ stdenv.lib.optionals stdenv.cc.isClang [ "CC=clang" "LD=clang" ];
 
   installPhase = ''
     mkdir -p $out/bin
diff --git a/pkgs/tools/misc/ent/default.nix b/pkgs/tools/misc/ent/default.nix
index d6ad7f1d26b..71b4ec338df 100644
--- a/pkgs/tools/misc/ent/default.nix
+++ b/pkgs/tools/misc/ent/default.nix
@@ -14,6 +14,8 @@ stdenv.mkDerivation rec {
 
   buildInputs = [ unzip ];
 
+  buildFlags = if stdenv.cc.isClang then [ "CC=clang" ] else null;
+
   installPhase = ''
     mkdir -p $out/bin
     cp ent $out/bin/
diff --git a/pkgs/tools/networking/bwm-ng/default.nix b/pkgs/tools/networking/bwm-ng/default.nix
index 62dea1e6cd4..6fa0c20b0ac 100644
--- a/pkgs/tools/networking/bwm-ng/default.nix
+++ b/pkgs/tools/networking/bwm-ng/default.nix
@@ -7,9 +7,12 @@ stdenv.mkDerivation rec {
     url = "http://www.gropp.org/bwm-ng/${name}.tar.gz";
     sha256 = "1pgzc8y2y73n72qvbd2g0dkbkw5h0f83k5h9id1rsck8w9c464y1";
   };
-  
+
   buildInputs = [ ncurses ];
 
+  # This code uses inline in the gnu89 sense: see http://clang.llvm.org/compatibility.html#inline
+  NIX_CFLAGS_COMPILE = if stdenv.cc.isClang then "-std=gnu89" else null;
+
   meta = with stdenv.lib; {
     description = "A small and simple console-based live network and disk io bandwidth monitor";
     homepage = "http://www.gropp.org/?id=projects&sub=bwm-ng";
diff --git a/pkgs/tools/networking/curl/7.15.nix b/pkgs/tools/networking/curl/7.15.nix
index 2b13437d95c..4e533878ec1 100644
--- a/pkgs/tools/networking/curl/7.15.nix
+++ b/pkgs/tools/networking/curl/7.15.nix
@@ -75,6 +75,6 @@ stdenv.mkDerivation rec {
   meta = {
     homepage = "http://curl.haxx.se/";
     description = "A command line tool for transferring files with URL syntax";
-    platforms = stdenv.lib.platforms.all;
+    platforms = with stdenv.lib.platforms; allBut darwin;
   };
 }