treewide: add emulator to platform

You can use stdenv.hostPlatform.emulator to get an executable that
runs cross-built binaries. This could be any emulator. For instance,
we use QEMU to emulate Linux targets and Wine to emulate Windows
targets. To work with qemu, we need to support custom targets.

I’ve reworked the cross tests in pkgs/test/cross to use this
functionality.

Also, I’ve used talloc to cross-execute with the emulator. There
appears to be a cross-execute for all waf builds. In the future, it
would be nice to set this for all waf builds.

Adds stdenv.hostPlatform.qemuArch attrbute to get the qemuArch for
each platform.

lib/systems/default.nix

@@ -66,6 +66,46 @@ rec {
          # uname -r
          release = null;
       };
+
+      qemuArch =
+        if final.isArm then "arm"
+        else if final.isx86_64 then "x86_64"
+        else if final.isx86 then "i386"
+        else {
+          "powerpc" = "ppc";
+          "powerpc64" = "ppc64";
+          "powerpc64le" = "ppc64";
+          "mips64" = "mips";
+          "mipsel64" = "mipsel";
+        }.${final.parsed.cpu.name} or final.parsed.cpu.name;
+
+      emulator = pkgs: let
+        qemu-user = pkgs.qemu.override {
+          smartcardSupport = false;
+          spiceSupport = false;
+          openGLSupport = false;
+          virglSupport = false;
+          vncSupport = false;
+          gtkSupport = false;
+          sdlSupport = false;
+          pulseSupport = false;
+          smbdSupport = false;
+          seccompSupport = false;
+          hostCpuTargets = ["${final.qemuArch}-linux-user"];
+        };
+        wine-name = "wine${toString final.parsed.cpu.bits}";
+        wine = (pkgs.winePackagesFor wine-name).minimal;
+      in
+        if final.parsed.kernel.name == pkgs.stdenv.hostPlatform.parsed.kernel.name &&
+           (final.parsed.cpu.name == pkgs.stdenv.hostPlatform.parsed.cpu.name ||
+            (final.platform.isi686 && pkgs.stdenv.hostPlatform.isx86_64))
+        then pkgs.runtimeShell
+        else if final.isWindows
+        then "${wine}/bin/${wine-name}"
+        else if final.isLinux && pkgs.stdenv.hostPlatform.isLinux
+        then "${qemu-user}/bin/qemu-${final.qemuArch}"
+        else throw "Don't know how to run ${final.config} executables.";
+
     } // mapAttrs (n: v: v final.parsed) inspect.predicates
       // args;
   in assert final.useAndroidPrebuilt -> final.isAndroid;

pkgs/applications/virtualization/qemu/default.nix

@@ -18,6 +18,10 @@
 , virglSupport ? openGLSupport, virglrenderer
 , smbdSupport ? false, samba
 , hostCpuOnly ? false
+, hostCpuTargets ? (if hostCpuOnly
+                    then (stdenv.lib.optional stdenv.isx86_64 "i386-softmmu"
+                          ++ ["${stdenv.hostPlatform.qemuArch}-softmmu"])
+                    else null)
 , nixosTestRunner ? false
 }:
 
@@ -27,11 +31,6 @@ let
     + optionalString pulseSupport "pa,"
     + optionalString sdlSupport "sdl,";
 
-  hostCpuTargets = if stdenv.isx86_64 then "i386-softmmu,x86_64-softmmu"
-                   else if stdenv.isi686 then "i386-softmmu"
-                   else if stdenv.isAarch32 then "arm-softmmu"
-                   else if stdenv.isAarch64 then "aarch64-softmmu"
-                   else throw "Don't know how to build a 'hostCpuOnly = true' QEMU";
 in
 
 stdenv.mkDerivation rec {
@@ -113,7 +112,7 @@ stdenv.mkDerivation rec {
     ++ optional smartcardSupport "--enable-smartcard"
     ++ optional spiceSupport "--enable-spice"
     ++ optional usbredirSupport "--enable-usb-redir"
-    ++ optional hostCpuOnly "--target-list=${hostCpuTargets}"
+    ++ optional (hostCpuTargets != null) "--target-list=${stdenv.lib.concatStringsSep "," hostCpuTargets}"
     ++ optional stdenv.isDarwin "--enable-cocoa"
     ++ optional stdenv.isLinux "--enable-linux-aio"
     ++ optional gtkSupport "--enable-gtk"
@@ -135,12 +134,13 @@ stdenv.mkDerivation rec {
     '';
 
   # Add a ‘qemu-kvm’ wrapper for compatibility/convenience.
-  postInstall =
+  postInstall = ''
-    if stdenv.isx86_64       then ''makeWrapper $out/bin/qemu-system-x86_64  $out/bin/qemu-kvm --add-flags "\$([ -e /dev/kvm ] && echo -enable-kvm)"''
+    if [ -x $out/bin/qemu-system-${stdenv.hostPlatform.qemuArch} ]; then
-    else if stdenv.isi686    then ''makeWrapper $out/bin/qemu-system-i386    $out/bin/qemu-kvm --add-flags "\$([ -e /dev/kvm ] && echo -enable-kvm)"''
+      makeWrapper $out/bin/qemu-system-${stdenv.hostPlatform.qemuArch} \
-    else if stdenv.isAarch32 then ''makeWrapper $out/bin/qemu-system-arm     $out/bin/qemu-kvm --add-flags "\$([ -e /dev/kvm ] && echo -enable-kvm)"''
+                  $out/bin/qemu-kvm \
-    else if stdenv.isAarch64 then ''makeWrapper $out/bin/qemu-system-aarch64 $out/bin/qemu-kvm --add-flags "\$([ -e /dev/kvm ] && echo -enable-kvm)"''
+                  --add-flags "\$([ -e /dev/kvm ] && echo -enable-kvm)"
-    else "";
+    fi
+  '';
 
   passthru = {
     qemu-system-i386 = "bin/qemu-system-i386";

pkgs/development/libraries/talloc/default.nix

@@ -1,5 +1,6 @@
 { stdenv, fetchurl, python, pkgconfig, readline, libxslt
 , docbook_xsl, docbook_xml_dtd_42, fixDarwinDylibNames
+, buildPackages
 }:
 
 stdenv.mkDerivation rec {
@@ -10,10 +11,9 @@ stdenv.mkDerivation rec {
     sha256 = "1kk76dyav41ip7ddbbf04yfydb4jvywzi2ps0z2vla56aqkn11di";
   };
 
-  nativeBuildInputs = [ pkgconfig fixDarwinDylibNames ];
+  nativeBuildInputs = [ pkgconfig fixDarwinDylibNames python
-  buildInputs = [
+                        docbook_xsl docbook_xml_dtd_42 ];
-    python readline libxslt docbook_xsl docbook_xml_dtd_42
+  buildInputs = [ readline libxslt ];
-  ];
 
   prePatch = ''
     patchShebangs buildtools/bin/waf
@@ -23,10 +23,14 @@ stdenv.mkDerivation rec {
     "--enable-talloc-compat1"
     "--bundled-libraries=NONE"
     "--builtin-libraries=replace"
+  ] ++ stdenv.lib.optionals (stdenv.hostPlatform != stdenv.buildPlatform) [
+    "--cross-compile"
+    "--cross-execute=${stdenv.hostPlatform.emulator buildPackages}"
   ];
+  configurePlatforms = [];
 
   postInstall = ''
-    ar q $out/lib/libtalloc.a bin/default/talloc_[0-9]*.o
+    ${stdenv.cc.targetPrefix}ar q $out/lib/libtalloc.a bin/default/talloc_[0-9]*.o
   '';
 
   meta = with stdenv.lib; {

pkgs/test/cross/default.nix

@@ -1,12 +1,11 @@
-{ pkgs, pkgsCross, lib }:
+{ pkgs, lib }:
 
 let
 
-  emulators = {
+  testedSystems = lib.filterAttrs (name: value: let
-    mingw32 = "WINEDEBUG=-all ${pkgs.winePackages.minimal}/bin/wine";
+    platform = lib.systems.elaborate value;
-    mingwW64 = "WINEDEBUG=-all ${pkgs.wineWowPackages.minimal}/bin/wine";
+  in platform.isLinux || platform.isWindows
-    # TODO: add some qemu-based emulaltors here
+  ) lib.systems.examples;
-  };
 
   getExecutable = pkgs: pkgFun: exec:
     "${pkgFun pkgs}${exec}${pkgs.hostPlatform.extensions.executable}";
@@ -17,6 +16,10 @@ let
   in pkgs.runCommand "test-${pkgName}-${crossPkgs.hostPlatform.config}" {
     nativeBuildInputs = [ pkgs.dos2unix ];
   } ''
+    # Just in case we are using wine, get rid of that annoying extra
+    # stuff.
+    export WINEDEBUG=-all
+
     HOME=$(pwd)
     mkdir -p $out
 
@@ -44,29 +47,29 @@ let
     fi
   '';
 
+  mapMultiPlatformTest = test: lib.mapAttrs (name: system: test rec {
+    crossPkgs = import pkgs.path {
+      localSystem = { inherit (pkgs.hostPlatform) config; };
+      crossSystem = system;
+    };
+
+    emulator = crossPkgs.hostPlatform.emulator pkgs;
+
+    # Apply some transformation on windows to get dlls in the right
+    # place. Unfortunately mingw doesn’t seem to be able to do linking
+    # properly.
+    platformFun = pkg: if crossPkgs.hostPlatform.isWindows then
+      pkgs.buildEnv {
+        name = "${pkg.name}-winlinks";
+        paths = [pkg] ++ pkg.buildInputs;
+      } else pkg;
+  }) testedSystems;
+
 in
 
-lib.mapAttrs (name: emulator: let
+lib.mapAttrs (_: mapMultiPlatformTest) {
-  crossPkgs = pkgsCross.${name};
 
-  # Apply some transformation on windows to get dlls in the right
+  file = {platformFun, crossPkgs, emulator}: compareTest {
-  # place. Unfortunately mingw doesn’t seem to be able to do linking
-  # properly.
-  platformFun = pkg: if crossPkgs.hostPlatform.isWindows then
-    pkgs.buildEnv {
-      name = "${pkg.name}-winlinks";
-      paths = [pkg] ++ pkg.buildInputs;
-    } else pkg;
-in {
-
-  hello = compareTest {
-    inherit emulator crossPkgs;
-    hostPkgs = pkgs;
-    exec = "/bin/hello";
-    pkgFun = pkgs: pkgs.hello;
-  };
-
-  file = compareTest {
     inherit emulator crossPkgs;
     hostPkgs = pkgs;
     exec = "/bin/file";
@@ -77,4 +80,11 @@ in {
     pkgFun = pkgs: platformFun pkgs.file;
   };
 
-}) emulators
+  hello = {platformFun, crossPkgs, emulator}: compareTest {
+    inherit emulator crossPkgs;
+    hostPkgs = pkgs;
+    exec = "/bin/hello";
+    pkgFun = pkgs: pkgs.hello;
+  };
+
+}

pkgs/top-level/all-packages.nix

@@ -12465,7 +12465,7 @@ with pkgs;
   taglib-sharp = callPackage ../development/libraries/taglib-sharp { };
 
   talloc = callPackage ../development/libraries/talloc {
-    python = python2;
+    python = buildPackages.python2;
   };
 
   tclap = callPackage ../development/libraries/tclap {};