[Bug-kawa] [bug #36335] NPE on syntax error

[Charles H. Turner]

URL:
  <http://savannah.gnu.org/bugs/?36335>

                 Summary: NPE on syntax error
                 Project: Kawa
            Submitted by: charlest
            Submitted on: Sun 29 Apr 2012 11:17:42 AM GMT
                Category: Scheme language
                Severity: 3 - Normal
              Item Group: Run-time exception
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any

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Details:

The following should output a syntax error rather than a NPE:

#|kawa:1|# (zero? (define-simple-class))
java.lang.NullPointerException
       at kawa.standard.define_class.rewriteForm(define_class.java:122)
...

Jamison investigated this on the mailing lists:

"The cause is that define_class#rewriteForm() does this:

   Declaration decl = null;
   Object form_cdr = form.getCdr(); // form is the list (define-simple-class),
so form_cdr is ()
   if (form_cdr instanceof Pair)    // and () is not a pair, so we skip
directly to line 122
     {
       ...
     }
   ClassExp oexp = (ClassExp) decl.getValue(); // here, where decl is still
null, triggering the NPE


So that if statement should probably have an else clause, something like

   else
   {
     return tr.syntaxError(this.getName() + ": missing class name");
   }

or maybe "else if (form_cdr == EmptyList.emptyList) { ... } else {...}"
so other bad syntax like "(define-simple-class . 42)" can have a different
error message."

Just needs to be patched. I'll do this eventually, putting it on Savannah so
that it's not forgotten.




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