Re: Kawa 1.13 compilation problem, possible regression

[Per Bothner <per at bothner dot com>]

On 05/04/2013 08:32 PM, Matthieu Vachon wrote:
> Hi Per,
>
> I tried to compile latest version (r7491) but was not able to do so
> under java5. With java6, it went well and didn't hit any problems.
> Here the failing bit when compiling with java5:
>
> [kawac] (compiling c:\Nu\kawa\kawa\lib\rnrs\unicode.scm to
> kawa.lib.rnrs.unicode)
> [kawac] c:\Nu\kawa\kawa\lib\rnrs\unicode.scm:117:11: unreachable procedure call
> [kawac] c:\Nu\kawa\kawa\lib\rnrs\unicode.scm:117:11: note - this
> operand never finishes
> [kawac] c:\Nu\kawa\kawa\lib\rnrs\unicode.scm:117:11: unreachable procedure call
> [kawac] c:\Nu\kawa\kawa\lib\rnrs\unicode.scm:117:11: note - this
> operand never finishes
> [kawac] c:\Nu\kawa\kawa\lib\rnrs\unicode.scm:117:11: unreachable procedure call
> [kawac] c:\Nu\kawa\kawa\lib\rnrs\unicode.scm:117:11: note - this
> operand never finishes
> [kawac] c:\Nu\kawa\kawa\lib\rnrs\unicode.scm:117:11: unreachable procedure call
> [kawac] c:\Nu\kawa\kawa\lib\rnrs\unicode.scm:117:11: note - this
> operand never finishes
>
> I checked the code in `unicode.scm` but could find something wrong
> from my point of view.

The reason is that on java5 the cond-expand tag
string-normalize-unicode is false, so we get the equivalent of:

(define (string-normalize-nfd (str :: string)) :: string
  (error "unicode string normalization not available"))

The complaint is that the never-returns value of is incompatible
with the return value of string.  Which is true - but we should
allow it anyway.  And that was the intention, but there was
a little bug - incorrect variable reuse.  Should be fixed
in the attached patch.
--
	--Per Bothner
per@bothner.com   http://per.bothner.com/

Index: gnu/expr/ChainLambdas.java
===================================================================
--- gnu/expr/ChainLambdas.java	(revision 7491)
+++ gnu/expr/ChainLambdas.java	(working copy)
@@ -50,21 +50,21 @@
     }
 
     protected Expression visitApplyExp(ApplyExp exp, ScopeExp scope) {
-        Expression e = visit(exp.func, scope);
+        Expression f = visit(exp.func, scope);
         Expression[] args = exp.args;
         int nargs = args.length;
-        exp.func = e;
-        if (e.neverReturns()) {
+        exp.func = f;
+        if (f.neverReturns()) {
             maybeWarnUnreachable(nargs > 0 ? args[0] : exp);
-            return e;
+            return f;
         }
         for (int i = 0; i < nargs;  i++) {
-            e = visit(args[i], scope);
+            Expression e = visit(args[i], scope);
             if (e.neverReturns()
                 // It seems best to silently allow converting never-returns
                 // to any type.  For example it useful for stub procedures
                 // that throw an "unimplemented" exception.
-                && ! (e.valueIfConstant() instanceof Convert)) {
+                && ! (f.valueIfConstant() instanceof Convert)) {
                 Expression[] xargs = new Expression[i+2];
                 xargs[0] = exp.func;
                 System.arraycopy(args, 0, xargs, 1, i+1);