Consider the following class:
class Debugging {
public static void main(String[] args) {
a: if (args.length > 0) {
b: println "args"
}
}
}
And let's say that I run the program with no arguments, and I put IntelliJ
debugger to break on line a. Now when I "step next" I see it highlight line b,
then step next and the program ends. The line b clearly did not run. Is this a
problem with IntelliJ or the bytecode? Below is the bytecode for the method.
I'm assuming the issue is that L2 is before the return, and at the return
bytecode we see before it LINENUMBER 4. If the return was annotated with a
linenumber 5 or 6, I assume the debugger would step to the closing brace of the
if statement (or of the method itself, depending on what was preferred). Is
this an issue with the IntelliJ debugger, or is it really a limitation of the
Groovy bytecode generation? A workaround is if I put an empty return statement
at the end of main, the debugger works, but strangely in bytecode I see two
returns.
public static transient varargs main([Ljava/lang/String;)V
L0
INVOKESTATIC Debugging.$getCallSiteArray
()[Lorg/codehaus/groovy/runtime/callsite/CallSite;
ASTORE 1
L1
LINENUMBER 3 L1
ALOAD 1
LDC 0
AALOAD
ALOAD 0
INVOKEINTERFACE
org/codehaus/groovy/runtime/callsite/CallSite.callGetProperty
(Ljava/lang/Object;)Ljava/lang/Object;
ICONST_0
INVOKESTATIC java/lang/Integer.valueOf (I)Ljava/lang/Integer;
INVOKESTATIC
org/codehaus/groovy/runtime/ScriptBytecodeAdapter.compareGreaterThan
(Ljava/lang/Object;Ljava/lang/Object;)Z
IFEQ L2
L3
LINENUMBER 4 L3
ALOAD 1
LDC 1
AALOAD
LDC LDebugging;.class
LDC "args"
INVOKEINTERFACE org/codehaus/groovy/runtime/callsite/CallSite.callStatic
(Ljava/lang/Class;Ljava/lang/Object;)Ljava/lang/Object;
POP
L2
RETURN
LOCALVARIABLE args [Ljava/lang/String; L0 L2 0
MAXSTACK = 3
MAXLOCALS = 2
Jason Winnebeck
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