Enabling 64-bit mojo shell to launch 32-bit child to handle nonsfi content.

services/nacl/BUILD.gn

Index: services/nacl/BUILD.gn
diff --git a/services/nacl/BUILD.gn b/services/nacl/BUILD.gn
index 37f2515b7321959933eff0fd298ece9796977d34..c8ed5192a3be9f914648ba3fc6b9b408dbcb4d7c 100644
--- a/services/nacl/BUILD.gn
+++ b/services/nacl/BUILD.gn
@@ -26,20 +26,52 @@ if (!is_nacl) {
     data_deps = [ "//nacl_bindings:irt_mojo(//native_client/build/toolchain/nacl:irt_${target_cpu})" ]
   }
 
-  mojo_native_application("nacl_content_handler_nonsfi") {
-    sources = [
-      "content_handler_main_nonsfi.cc",
-    ]
+  if (current_cpu == "x86") {
+    # Nonsfi nacl can only be executed by a 32-bit process, so our

[Petr Hosek, 2015/09/14 19:13:51]

Nit: "Non-SFI NaCl" instead of "Nonsfi nacl".

[Sean Klein, 2015/09/15 18:37:50]

Done.

+    # content handler must be built and launched as a 32-bit process as well.
+    mojo_native_application("nacl_content_handler_nonsfi") {
+      sources = [
+        "content_handler_main_nonsfi.cc",
+      ]
 
-    deps = [
-      "//base",
-      "//mojo/application:application",
-      "//mojo/application:content_handler",
-      "//mojo/data_pipe_utils",
-      "//mojo/message_pump",
-      "//mojo/nacl:irt_mojo_nonsfi",
-      "//mojo/public/cpp/application:application",
-      "//native_client/src/nonsfi/loader:elf_loader",
-    ]
+      deps = [
+        "//base",
+        "//mojo/application:application",
+        "//mojo/application:content_handler",
+        "//mojo/data_pipe_utils",
+        "//mojo/message_pump",
+        "//mojo/nacl:irt_mojo_nonsfi",
+        "//mojo/public/cpp/application:application",
+        "//native_client/src/nonsfi/loader:elf_loader",
+      ]
+    }
+
+    # Copy to the root build directory so our content handler prefixed line

[Mark Seaborn, 2015/09/14 18:38:58]

How about: "so that the '#!' prefix line for invoking our content handler..."
(easier to parse)

[Sean Klein, 2015/09/15 18:37:50]

Done.

+    # can simply be "mojo:nacl_content_handler_nonsfi".
+    if ("${root_out_dir}" != "${root_build_dir}") {

[Petr Hosek, 2015/09/14 19:13:51]

Do you really need this? To check that you're not using a default toolchain you
should use `current_toolchain != default_toolchain`.

[Sean Klein, 2015/09/15 18:37:50]

I updated things to use a different naming convention. This conditional is no
longer here.

Since you suggested renaming the group to "nacl_content_handler_nonsfi", I
renamed the native application to "nacl_content_handler_nonsfi_x86" (since it is
always built as 32 bit). 

The copy rule is now always used, on both 32 and 64 bit systems, to copy
".../nacl_content_handler_nonsfi_x86.mojo" to
".../nacl_content_handler_nonsfi.mojo".

+      copy("nacl_content_handler_nonsfi_copy") {
+        sources = [
+          "${root_out_dir}/nacl_content_handler_nonsfi.mojo",
+        ]
+        outputs = [
+          "${root_build_dir}/{{source_file_part}}",
+        ]
+        deps = [
+          ":nacl_content_handler_nonsfi",
+        ]
+      }
+    }
+  }
+}
+
+# This group serves as a 64 to 32 bit transformation for Linux. If we are
+# using a 64 bit toolchain, build the nonsfi nacl content handler as 32 bit.
+group("nacl_content_handler_nonsfi_x86") {

[Petr Hosek, 2015/09/14 19:13:51]

I'd suggest naming the group `nacl_content_handler_nonsfi` since you'll likely
use it to handle ARM (32-bit vs 64-bit) as well.

[Sean Klein, 2015/09/15 18:37:50]

Done.

+  deps = []
+  if (target_cpu == "x64" && is_linux) {
+    deps += [ ":nacl_content_handler_nonsfi_copy(//build/toolchain/linux:clang_x86)" ]

[Mark Seaborn, 2015/09/14 18:38:58]

See other comment -- comment to warn about assuming clang here?

[Sean Klein, 2015/09/15 18:37:50]

Done.

+  } else if (target_cpu == "x86" && is_linux) {
+    deps +=
+        [ ":nacl_content_handler_nonsfi(//build/toolchain/linux:clang_x86)" ]

[Petr Hosek, 2015/09/14 19:13:51]

What if the default toolchain is glibc_x86? Then the `target_cpu == "x86"` but
the nacl_content_handler_nonsfi binary will end up in `$root_out_dir` since
you're not using the default toolchain and you still need to copy it to
`$root_build_dir`.

[Sean Klein, 2015/09/15 18:37:50]

Although this is untested, the new dependency on the copy rule (regardless of
x86 vs x64) should cause the binary to be copied to the root_out_dir regardless
of default toolchain. I think.

   }
 }