Sort the Dart vm flags before printing them out with the --print-flags option.

runtime/vm/flags.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/flags.h"
 
 #include "platform/assert.h"
 #include "vm/os.h"
 
 namespace dart {
@@ skipping 283 matching lines @@
         unrecognized_count++;
       }
       flag = flag->next_;
     }
     if (unrecognized_count > 0) {
       OS::PrintErr("\n");
       exit(255);
     }
   }
   if (FLAG_print_flags) {
-    OS::Print("Flag settings:\n");
-    Flag* flag = Flags::flags_;
-    while (flag != NULL) {
-      flag->Print();
-      flag = flag->next_;
-    }
+    PrintFlags();
   }
-
   return true;
 }
 
+
+int Flags::CompareFlagNames(const void* left, const void* right) {
+  const Flag* left_flag = *reinterpret_cast<const Flag* const *>(left);
+  const Flag* right_flag = *reinterpret_cast<const Flag* const *>(right);
+  return strcmp(left_flag->name_, right_flag->name_);
+}
+
+
+void Flags::PrintFlags() {
+    OS::Print("Flag settings:\n");
+    Flag* flag = Flags::flags_;
+    int num_flags = 0;
+    while (flag != NULL) {
+      num_flags++;

[Ivan Posva, 2012/08/20 23:50:35]

You could increment this as part of registration of flags and keep it around
with the rest of the flags. Although I am not sure of the usefulness of the
count beyond PrintFlags.

+      flag = flag->next_;
+    }
+    Flag** flag_array = new Flag*[num_flags];
+    flag = Flags::flags_;
+    int flag_index = 0;
+    while (flag != NULL) {

[Ivan Posva, 2012/08/20 23:50:35]

for (int i = 0; i <  num_flags; i++) {
  ASSERT(flag != NULL);
  flag_array[i] = flag;
  flag = flag->next_;
}
ASSERT(flag = NULL);

To be consistent with the other loop going over the flags array.
You could also put the flag = flag->next_ into the for-loop. I am not a big fan
of multiple things happening there, but in this case it almost makes sense.

[Bill Hesse, 2012/08/21 09:21:02]

Done.

+      flag_array[flag_index] = flag;
+      flag_index++;
+      flag = flag->next_;
+    }
+
+    qsort(flag_array, num_flags, sizeof flag_array[0], CompareFlagNames);
+
+    for (int i = 0; i < num_flags; ++i) {
+      flag_array[i]->Print();
+    }
+    delete[] flag_array;
+  }
 }  // namespace dart