Summary

Update the spec of StackFrame::getByteCodeIndex to return negative value when BCI is not available.

Problem

There are odd cases in the JITs that BCI is invalid. For example, a synchronized method has no explicit monitorenter bytecode. Since the action can block, you can hit a safepoint on BCI #0 either before or after the monitor is locked.

Solution

Change the spec of StackFrame::getByteCodeIndex to return negative value when BCI is not available.

Specification

The spec of java.lang.StackWalker.StackFrame::getByteCodeIndex is modified as follows:

diff --git a/src/java.base/share/classes/java/lang/StackWalker.java b/src/java.base/share/classes/java/lang/StackWalker.java
--- a/src/java.base/share/classes/java/lang/StackWalker.java
+++ b/src/java.base/share/classes/java/lang/StackWalker.java
@@ -178,7 +178,7 @@
          *
          * @return the index to the code array of the {@code Code} attribute
          *         containing the execution point represented by this stack frame,
-         *         or a negative number if the method is native.
+         *         or a negative number if the method is native or unavailable.
          *
          * @jvms 4.7.3 The {@code Code} Attribute
          */