Fix issue 825 (LiveEdit vs. function with no locals) in core and for ia32.

src/debug.h

Index: src/debug.h
diff --git a/src/debug.h b/src/debug.h
index 7ec78015c6d2d65794b8f0f299444ccf570683b2..2ab3f2ae5d033328b984995fa3fb25902ec80dc0 100644
--- a/src/debug.h
+++ b/src/debug.h
@@ -457,6 +457,49 @@ class Debug {
   // Architecture-specific constant.
   static const bool kFrameDropperSupported;
 
+  /**
+   * Defines layout of a stack frame that supports padding. This is a regular
+   * internal frame that has a flexible stack structure. LiveEdit can shift
+   * its lower part up the stack, taking up the 'padding' space when additional
+   * stack memory is required.
+   * Such frame is expected immediately above the topmost JavaScript frame.
+   *
+   * Stack Layout:
+   *   --- Top
+   *   LiveEdit routine frames
+   *   ---
+   *   C frames of debug handler
+   *   ---
+   *   ...
+   *   ---
+   *      An internal frame that has n padding words:
+   *      - any number of words as needed by code -- upper part of frame
+   *      - padding size: a Smi storing n -- current size of padding
+   *      - padding: n words filled with kPaddingValue in form of Smi
+   *      - 3 context/type words of a regular InternalFrame
+   *      - fp
+   *   ---
+   *      Topmost JavaScript frame
+   *   ---
+   *   ...
+   *   --- Bottom
+   */
+  struct FramePaddingLayout : public AllStatic {

[Yang, 2012/05/03 14:00:47]

Even though not actually necessary, please make this a class (instead of struct)
for consistency's sake.

[Peter Rybin, 2012/05/03 17:07:11]

Done.

+    // Architecture-specific constant.
+    static const bool kIsSupported;
+
+    // A size of frame base including fp. Padding words starts right above
+    // the base.
+    static const int kFrameBaseSize = 4;
+
+    // A number of words that should be reserved on stack for the LiveEdit use.
+    // Normally equals 1. Stored on stack in form of Smi.
+    static const int kInitialSize;
+    // A value that padding words are filled with (in form of Smi). Going
+    // bottom-top, the first word not having this value is a counter word.
+    static const int kPaddingValue;
+  };
+
  private:
   explicit Debug(Isolate* isolate);
   ~Debug();