Add native extensions for the Dart shell to mac and windows

runtime/bin/extensions_macos.cc

Index: runtime/bin/extensions_macos.cc
diff --git a/runtime/bin/extensions_macos.cc b/runtime/bin/extensions_macos.cc
index d81e670eef10218fe7bc68228faa4d0d88a9083c..2d2788ee205597fa84b565cfd21af37224222a45 100644
--- a/runtime/bin/extensions_macos.cc
+++ b/runtime/bin/extensions_macos.cc
@@ -3,12 +3,17 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include "bin/extensions.h"
+#include <dlfcn.h>
 
-#include "include/dart_api.h"
-#include "platform/assert.h"
+void* Extensions::LoadExtensionLibrary(const char* library_name) {
+  char* library_path = MakeString("./%s.so", library_name);

[Mads Ager (google), 2012/03/07 14:31:48]

lib%s.so?

Either that or remove the lib prefix on linux.

[Ivan Posva, 2012/03/07 19:06:23]

Please do not use .so extensions on Mac OS X. It is definitely not the right
extension. The equivalent of .so on Mac OS X is .dylib.

[Bill Hesse, 2012/03/08 12:04:37]

libfoo.so on linux and foo.dll on windows is the naming system that is
universally used by almost everyone doing cross-platform libraries and
extensions.  On mac, Python and gyp do foo.so, and people making shared
libraries (not bundles) do libfoo.dylib (but we aren't making dylibs).
Can we get some consensus on the naming?  I really feel we should go with what
gyp produces.



On 2012/03/07 14:31:48, Mads Ager wrote:

[Bill Hesse, 2012/03/08 12:04:37]

This is not a .dylib.  This is a bundle, not a shared library.  These are never
called .dylib.

Gyp and Python call their bundles .so.  The Apple documentation says they can
have any extension that you choose, like .bundle or one that your application
chooses.
Our make build chooses the extension .dylib for dynamic libraries and .so for
bundles.

+  void* lib_handle = dlopen(library_path, RTLD_LAZY);
+  delete[] library_path;
+  return lib_handle;
+}
 
-Dart_Handle Extensions::LoadExtension(const char* extension_url,
-                                      Dart_Handle parent_library) {
-  UNIMPLEMENTED();
-  return NULL;
+void* Extensions::ResolveSymbol(void* lib_handle, const char* symbol) {
+  void* result = dlsym(lib_handle, symbol);
+  if (dlerror() != NULL) return NULL;
+  return result;
 }