erlang: patch all versions to work with clang 4

pkgs/development/interpreters/erlang/R16.nix

@@ -27,6 +27,11 @@ stdenv.mkDerivation rec {
       ++ optional odbcSupport unixODBC
       ++ optionals stdenv.isDarwin [ Carbon Cocoa ];
 
+  # Clang 4 (rightfully) thinks signed comparisons of pointers with NULL are nonsense
+  prePatch = ''
+    substituteInPlace lib/wx/c_src/wxe_impl.cpp --replace 'temp > NULL' 'temp != NULL'
+  '';
+
   patchPhase = '' sed -i "s@/bin/rm@rm@" lib/odbc/configure erts/configure '';
 
   preConfigure = ''

pkgs/development/interpreters/erlang/R16B02-8-basho.nix

@@ -29,6 +29,11 @@ stdenv.mkDerivation rec {
       ++ optional odbcSupport [ unixODBC ]
       ++ optionals stdenv.isDarwin [ Carbon Cocoa ];
 
+  # Clang 4 (rightfully) thinks signed comparisons of pointers with NULL are nonsense
+  prePatch = ''
+    substituteInPlace lib/wx/c_src/wxe_impl.cpp --replace 'temp > NULL' 'temp != NULL'
+  '';
+
   patchPhase = '' sed -i "s@/bin/rm@rm@" lib/odbc/configure.in erts/configure.in '';
 
   preConfigure = ''

pkgs/development/interpreters/erlang/R17.nix

@@ -35,7 +35,12 @@ stdenv.mkDerivation rec {
       ++ optional javacSupport openjdk
       ++ stdenv.lib.optionals stdenv.isDarwin [ Carbon Cocoa ];
 
-  patchPhase = '' sed -i "s@/bin/rm@rm@" lib/odbc/configure erts/configure '';
+  patchPhase = ''
+    # Clang 4 (rightfully) thinks signed comparisons of pointers with NULL are nonsense
+    substituteInPlace lib/wx/c_src/wxe_impl.cpp --replace 'temp > NULL' 'temp != NULL'
+
+    sed -i "s@/bin/rm@rm@" lib/odbc/configure erts/configure
+  '';
 
   debugInfo = enableDebugInfo;
 

pkgs/development/interpreters/erlang/R18.nix

@@ -1,4 +1,4 @@
-{ stdenv, fetchurl, fetchFromGitHub, perl, gnum4, ncurses, openssl
+{ stdenv, fetchurl, fetchpatch, fetchFromGitHub, perl, gnum4, ncurses, openssl
 , gnused, gawk, autoconf, libxslt, libxml2, makeWrapper
 , Carbon, Cocoa
 , odbcSupport ? false, unixODBC ? null
@@ -53,6 +53,11 @@ stdenv.mkDerivation rec {
      sha256 = "10h5348p6g279b4q01i5jdqlljww5chcvrx5b4b0dv79pk0p0m9f";
   };
 
+  # Clang 4 (rightfully) thinks signed comparisons of pointers with NULL are nonsense
+  prePatch = ''
+    substituteInPlace lib/wx/c_src/wxe_impl.cpp --replace 'temp > NULL' 'temp != NULL'
+  '';
+
   patches = [
     rmAndPwdPatch
     envAndCpPatch

pkgs/development/interpreters/erlang/R19.nix

@@ -46,6 +46,9 @@ stdenv.mkDerivation rec {
   prePatch = ''
     substituteInPlace configure.in \
       --replace '`sw_vers -productVersion`' '10.10'
+
+    # Clang 4 (rightfully) thinks signed comparisons of pointers with NULL are nonsense
+    substituteInPlace lib/wx/c_src/wxe_impl.cpp --replace 'temp > NULL' 'temp != NULL'
   '';
 
   preConfigure = ''