Bug with Current KJC Compiler

[Brent Fulgham]

The version of KJC that ships in Kaffe right now has a bug with the ++ operator when used with instance variables.  Here's a sample program that highlights the problem (at least under a Cygwin build):

public class PlusPlusTest
{
	private int count = 0;

	public PlusPlusTest() {
		for (int i = 1; i < 5; ++i) {
				//count++;	// This works
				++count;	// This fails
		}
	}

	public static void main(String[] argv) {
		PlusPlusTest ppt = new PlusPlusTest();
		System.out.println("Test Key: " + new Integer(ppt.count).toString());
	}
}

An attempt to compile results in:

>>>>>>>>-1 / -2
10:	N/A	putfield
0:	1	aload_0
1:	0	invokespecial
2:	1	aload_0
3:	0	invokespecial
4:	1	iconst_1
5:	0	istore_1
6:	0	goto
7:	1	aload_0
8:	2	iconst_1
9:	1	iadd
10:	N/A	putfield
11:	N/A	iinc
12:	1	iload_1
13:	2	iconst_5
14:	0	if_icmplt
15:	N/A	return
0:	1	aload_0
1:	0	invokespecial
2:	1	aload_0
3:	0	invokespecial
4:	1	iconst_1
5:	0	istore_1
6:	0	goto
7:	1	aload_0
8:	2	iconst_1
9:	1	iadd
10:	N/A	putfield
11:	N/A	iinc
12:	1	iload_1
13:	2	iconst_5
14:	0	if_icmplt
15:	N/A	return
0:	1	aload_0
1:	0	invokespecial
2:	1	aload_0
3:	0	invokespecial
4:	1	iconst_1
5:	0	istore_1
6:	0	goto
7:	1	aload_0
8:	2	iconst_1
9:	1	iadd
10:	N/A	putfield
11:	N/A	iinc
12:	1	iload_1
13:	2	iconst_5
14:	0	if_icmplt
15:	N/A	return
GenCode failure in source class: PlusPlusTest
at.dms.classfile.ClassFileFormatException: stack underflow
	at at.dms.classfile.InstructionHandle.checkInstruction(InstructionHandle.java:122)
	at at.dms.classfile.CodeEnv.checkExecutionPath(CodeEnv.java:95)
	at at.dms.classfile.JumpInstruction.check(JumpInstruction.java:147)
	at at.dms.classfile.InstructionHandle.checkInstruction(InstructionHandle.java:133)
	at at.dms.classfile.CodeEnv.checkExecutionPath(CodeEnv.java:95)
	at at.dms.classfile.JumpInstruction.check(JumpInstruction.java:147)
	at at.dms.classfile.InstructionHandle.checkInstruction(InstructionHandle.java:133)
	at at.dms.classfile.CodeEnv.checkExecutionPath(CodeEnv.java:95)
	at at.dms.classfile.CodeEnv.checkExecutionPaths(CodeEnv.java:73)
	at at.dms.classfile.CodeEnv.check(CodeEnv.java:47)
	at at.dms.classfile.CodeInfo.resolveConstants(CodeInfo.java:289)
	at at.dms.classfile.AttributeList.resolveConstants(AttributeList.java:237)
	at at.dms.classfile.MethodInfo.resolveConstants(MethodInfo.java:221)
	at at.dms.classfile.ClassInfo.resolveConstants(ClassInfo.java:467)
	at at.dms.classfile.ClassInfo.write(ClassInfo.java:360)
	at at.dms.classfile.ClassInfo.write(ClassInfo.java:436)
	at at.dms.kjc.CSourceClass.genCode(CSourceClass.java:235)
	at at.dms.kjc.Main.genCode(Main.java:222)
	at at.dms.kjc.Main.run(Main.java:174)
	at at.dms.kjc.Main.compile(Main.java:68)
	at at.dms.kjc.Main.main(Main.java:59)
error:stack underflow

This happens under both Kaffe and the Sun JVM, so seems to indicate a bug in the actual KJC compiler code.

Under the new KJC (from their website), it works a bit better:

Administrator at BFULGHAM1 ~/java
$ javac PlusPlusTest.java
assertion "!INTS_DISABLED()" failed: file "exception.c", line 386
Aborted (core dumped)

I'm not sure which is worse -- however the second case indicates an issue with the JVM so might be of more interest to us as time passes.

Thanks,

-Brent