Re: [abc] Jastadd compile bugs

It doesn't surprise me that there are many bugs. The compilation
of Java is quite tricky, which is why the java2jimple translation
is tricky - and why we still find some bugs there.

Cheers, Laurie

+-----------------------------------------------------------------
| Laurie Hendren --- laurie.hendren@mcgill.ca
| Associate Dean (Academic), Faculty of Science,
| Dawson Hall, McGill University, 853 Sherbrooke St W,
| Montreal QC H3A 2T6 Canada, 514-398-7179, fax 514-398-1774
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On Thu, 12 Jan 2006, Neil Ongkingco wrote:

> I've attached one more jastadd bug. Note that the comments are just my
> best guesses on what the problem is, as I haven't really tried to debug
> the jastadd compiler code yet. As with the other examples, this compiles
> fine in both javac and abc.
>
> I'm getting the impression that there seems to be a good number of bugs
> that need fixing, and that it may not as yet be worth moving to jastadd.
> There are still some bugs that I haven't isolated yet (including a
> rather strange one that says "primitive.Illegal is not assignable to a
> variable of type primitive.Unknown"), so there may be more to come.
>
> Neil
>
> Pavel Avgustinov wrote:
>
> >Neil Ongkingco wrote:
> >
> >
> >
> >>Attached are some jastadd bugs found when compiling using Jigsaw.
> >>Perhaps they will help in deciding whether we should switch. All
> >>examples compile fine in both javac and abc. I'm still just halfway
> >>through jastadd's error dump, so I might add some more bugs later today.
> >>
> >>
> >>
> >Some remarks on the test cases below.
> >
> >
> >
> >>class CharByteTest {
> >> public static void main(String args[]) {
> >> byte a = 100;
> >> System.out.println("Hello world");
> >> //Jastadd does not properly recognize the cast, and insists
> >> //that the type of the expression is still a char
> >> a = (byte) (a - 'a');
> >> }
> >>}
> >>
> >>
> >>
> >>
> >The comment about the problem in JastAdd is misleading. It's not the
> >cast that confuses it; rather, it tries to add the byte a to the char
> >'a' without performing binary numeric promotion
> >(http://java.sun.com/docs/books/jls/second_edition/html/conversions.doc.html#170983),
> >i.e. without converting both to int first. Thus it ends up with
> >mismatched types on the '-' operation, not on the assignment back to a.
> >Casting the first operand to char or the second to byte ensures
> >compilability with jastadd. It is interesting that if one changes the
> >expression to "a = (char) a - 'a';", then jastadd complains that it
> >can't assign int to byte, i.e. it does do some promotion of its
> >arguments, but seemingly too late.
> >
> >
> >
> >>import java.io.*;
> >>
> >>class FinallyTest {
> >> //Jastadd gives a false error report if more than one exception
> >> //is specifified in the signature. Removing InterruptedException
> >> //allows Jastadd to compile properly
> >> public static void a() throws IOException, InterruptedException {
> >> throw new IOException("FinallyTest.a");
> >> }
> >>
> >> public static void main(String args[]) throws Exception{
> >> try {
> >> a();
> >> } finally {
> >> try {
> >> a();
> >> } catch (IOException e) {}
> >> }
> >> }
> >>}
> >>
> >>
> >>
> >>
> >This is indeed rather strange -- the error JastAdd reports is that the
> >body of the catch block is unreachable, and indeed this is reported
> >whenever a() is declared to throw more than one exception, whether or
> >not it is declared to throw IOException. No idea about this one.
> >
> >
> >
> >>class ClassTest {
> >> static {
> >> //Jastadd doesn't lookup names properly in static blocks
> >> Class c = ClassTest.class;
> >> }
> >> public static void main(String args[]) {
> >> }
> >>}
> >>
> >>
> >>
> >>
> >Again, the comment about the problem is misleading. The problem here is
> >in JastAdd-generated code. The exact error message is "*** Semantic
> >Error: variable class$ClassTest is used in static { Class c =
> >class$ClassTest != null ? class$ClassTest : class$ClassTest =
> >class$("ClassTest"); } before it is declared". Interestingly if one
> >drops the static block, this works correctly -- perhaps the (generated)
> >class$ClassTest variable isn't static itself?
> >
> >
> >
>
> >>class ClassTest2 {
> >> //Jastadd also has lookup problems for static variables
> >> static Class cn = ClassTest2.class;
> >> public static void main(String args[]) {
> >> }
> >>}
> >>
> >>
> >>
> >>
> >This is identical to above (in fact, though I may be wrong, I think the
> >bottom form is syntactic sugar for the top). It certainly produces the
> >same error message.
> >
> >
> >The problem me and Julian have been talking about is demonstrated by
> >this simple test case:
> >
> >public class Test {
> > public static void main(String[] args) {
> > StringBuffer b = new StringBuffer();
> > b.append('-');
> > }
> >}
> >
> >When compiled with a Java 1.4 JVM, this works fine. Under a Java5 JVM,
> >JastAdd can't compile it -- it complains about an uncaught IOException
> >on the call to append(). The reason is that the Java 5 API introduces an
> >Appendable interface with a method 'Appendable append(char c) throws
> >IOException', and StringBuffer implements Appendable. The method lookup
> >ends up returning the method from the interface rather than the
> >StringBuffer class, and so exception behaviour is considered incorrect.
> >This is actually quite nasty, because a lot of String manipulations get
> >compiled down to StringBuffer actions, so this prevents the compilation
> >of many many programs in a Java5 environment.
> >
> >I'll summarise any other problems in this thread; we should send it to
> >Torbjorn for comments/fixes when we've finalised it.
> >
> >- P
> >
> >
> >
> >
>
>
Received on Thu Jan 12 15:08:20 2006