Make Platform.executable return a fully qualified path the the executable

runtime/bin/platform.h

Index: runtime/bin/platform.h
diff --git a/runtime/bin/platform.h b/runtime/bin/platform.h
index 78cb33de62be8a4af4251feb7ee5d500e14f608f..6b81539da10433bb69f943b98eb2756d019479ba 100644
--- a/runtime/bin/platform.h
+++ b/runtime/bin/platform.h
@@ -39,11 +39,21 @@ class Platform {
   static char** Environment(intptr_t* count);
   static void FreeEnvironment(char** env, intptr_t count);
 
-  // Stores and gets the executable name.
+  static char* ResolveExecutablePath();
+
+  // Stores the executable name.
   static void SetExecutableName(const char* executable_name) {
     executable_name_ = executable_name;

[Lasse Reichstein Nielsen, 2015/05/20 10:48:43]

Should this set ..._resolved_ to true?

[Søren Gjesse, 2015/05/20 11:14:24]

This is being called from main() with the value of argv[0], which was what we
previously used for Platform.executable. This is still the fallback value is
somehow the system calls to find the absolute path fails.

   }
   static const char* GetExecutableName() {
+    if (!executable_name_resolved_) {
+      // Try to resolve the executable path using platform specific APIs.
+      char* path = Platform::ResolveExecutablePath();
+      if (path != NULL) {
+        executable_name_ = path;
+      }
+      executable_name_resolved_ = true;
+    }
     return executable_name_;
   }
 
@@ -68,7 +78,11 @@ class Platform {
   }
 
  private:
+  // The path to the executable.
   static const char* executable_name_;
+  // State to indicate whether the executable name has been resolved.
+  static bool executable_name_resolved_;

[Lasse Reichstein Nielsen, 2015/05/20 10:48:43]

Is this really necessary?
As opposed to just checking if executable_name_ is NULL?

The only difference is that we might try resolving more than once if it fails
resolving, which is probably fine.

I'd expect we could cache the result on the Dart side, and only call this
function once per isolate. It it returns null, I don't mind calling it again for
each isolate that cares, since that should rarely happen (right?).

[Søren Gjesse, 2015/05/20 11:14:24]

See above. We have a fallback to argv[0].

+
   static const char* package_root_;
   static int script_index_;
   static char** argv_;  // VM flags are argv_[1 ... script_index_ - 1]