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diff --git a/docs/debugger.html b/docs/debugger.html index 6e23f0df2..7d93caf08 100644 --- a/docs/debugger.html +++ b/docs/debugger.html @@ -202,6 +202,40 @@ list, even if the debugger never sees them. Having a debugger attached to a program that throws lots of exceptions can result in out-of-memory errors. This will be fixed in a future release. </p><p> + +</p><p> +The translation from Java bytecode to Dalvik bytecode may result in +identical sequences of instructions being combined. This can make it +look like the wrong bit of code is being executed. For example: +<pre> int test(int i) { + if (i == 1) { + return 0; + } + return 1; + }</pre> +The Dalvik bytecode uses a common <code>return</code> instruction for both +<code>return</code> statements, so when <code>i</code> is 1 the debugger +will single-step through <code>return 0</code> and then <code>return 1</code>. +</p><p> + +</p><p> +Dalvik handles synchronized methods differently from other VMs. +Instead of marking a method as <code>synchronized</code> and expecting +the VM to handle the locks, <code>dx</code> inserts a "lock" +instruction at the top of the method and an "unlock" instruction in a +synthetic <code>finally</code> block. As a result, when single-stepping +a <code>return</code> statement, the "current line" cursor may jump to +the last line in the method. +</p><p> +This can also affect the way the debugger processes exceptions. The +debugger may decide to break on an +exception based on whether that exception is "caught" or "uncaught". To +be considered uncaught, there must be no matching <code>catch</code> block +or <code>finally</code> clause between the current point of execution and +the top of the thread. An exception thrown within or below a synchronized +method will always be considered "caught", so the debugger won't stop +until the exception is re-thrown from the synthetic <code>finally</code> block. +</p><p> <address>Copyright © 2009 The Android Open Source Project</address> |