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Name: dkC59003 Date: 11/20/97
The document "Inner Classes in Java 1.1" says:
"For purposes of linking, the compiler must generate a unique externally
visible name for every inaccessible class. The overall form of
these names is a class name, followed by additional numbers or names, separated by $ characters.
Also, variable names synthesized by the compiler beginning with this$ and val$ must follow the usage patterns described here."
Compiler outputs an error while compiling the following source file
incorrectly considering val$prm2 as int whereas it is defined as Object.
Note that the case of val$prm1 is OK. The only difference between these two
variables is the parameter prm2 occurence preceding val$prm2 usage.
-----------------------------------------
package javasoft.sqe.tests.lang.icls122.icls12201;
import java.io.PrintStream;
public class icls12201 {
interface Intf {
int getFirst();
int getSecond();
}
static Intf meth(final int prm1, final int prm2) {
final Object val$prm1 = null;
final Object val$prm2 = null;
class InnClass implements Intf {
Object locVar;
public int getFirst() {
locVar = val$prm1;
return prm1;
}
public int getSecond() {
int locInt;
locInt = prm2;
locVar = val$prm2;
return locInt;
}
}
return new InnClass();
}
}
-----------------------------------------
JDK 1.1.5F and JDK 1.2S compilers output:
t1.java:26: Incompatible type for =. Can't convert int to java.lang.Object.
locVar = val$prm2;
^
1 error
-----------------------------------------
======================================================================
A similar problem can arise with the flatnames of inner classes
conflicting with explicitly-declared classes (from 4096303):
class Some$Clazz { }
class Some {
class Clazz { }
}
Another case was reported in 4030356:
Source code can refer to synthetic names like "this$Foo",
which are an implementation detail supposedly inaccessible to programmers.
Thus, files like this should not compile, but they do:
class HiddenFieldBug {
class Inner {
Object x = this$HiddenFieldBug;
// A similar problem exists with other synthesized names,
// such as val$foo, access$2(), HiddenFieldBug$1$Local.
}
}
william.maddox@Eng 2000-01-10
======================================================================
from 4094180:
Javac (jdk1.4.0beta-b62, jdk1.3.1-b23) allows access to a local
class by using a synthetic name that compiler constructs to represent
a local class. Through this synthetic name the class is accessible
even outside of its scope.
That contradicts the following assertions of JLS-2,
14.3 "Local class declarations":
"The scope of a local class declared in a block is the rest of the
immediately enclosing block, including its own class declaration."
"A local class does not have a canonical name, nor does it have a fully
qualified name."
The following test demonstrates the behavior:
--stmt16503_a.java--------------------------------------------
public class stmt16503_a {
public static void test() {
class Local {};
}
}
--------------------------------------------------------------
--stmt16503.java----------------------------------------------
public class stmt16503 {
public static void main(String argv[]) {
Object a = new stmt16503_a$1$Local();
}
}
--------------------------------------------------------------
The class Local can be accessed from a method of class stmt16503 by using
the name stmt16503_a$1$Local. To reproduce the bug classes should be compiled
in sequence - stmt16503_a.java, then stmt16503.java.
Compiler correctly detects the error when classes are compiled together.
The execution log is following:
$ jdk1.4.0beta-b62/solsparc/bin/java -version
java version "1.4.0-beta"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.0-beta-b62)
Java HotSpot(TM) Client VM (build 1.4.0-beta-b62, mixed mode)
$ jdk1.4.0beta-b62/solsparc/bin/javac -d . stmt16503_a.java stmt16503.java; echo
$?
stmt16503.java:3: cannot resolve symbol
symbol : class stmt16503_a$1$Local
location: class stmt16503
Object a = new stmt16503_a$1$Local();
^
1 error
1
$ jdk1.4.0beta-b62/solsparc/bin/javac -d . stmt16503_a.java; echo $?
0
$ jdk1.4.0beta-b62/solsparc/bin/javac -d . stmt16503.java; echo $?
0
$ jdk1.4.0beta-b62/solsparc/bin/java stmt16503; echo $?
0
$
========================================================
from 4480593:
When compiling the following class
class t
{
public static void main(String[] args)
{
Class c = t.class;
System.out.println(c);
}
int class$t() { return 0; }
}
the following exception trace was obtained.
C:\jdk1.4\bin>javac t.java
An exception has occurred in the compiler (1.4.0-beta). Please file a bug at the
Java Developer Connection (http://java.sun.com/cgi-bin/bugreport.cgi) after ch
ecking the Bug Parade for duplicates. Include your program and the following dia
gnostic in your report. Thank you.
java.lang.ClassCastException: com.sun.tools.javac.v8.code.Symbol$MethodSymbol
at com.sun.tools.javac.v8.comp.TransInner.cacheSym(TransInner.java:1528)
at com.sun.tools.javac.v8.comp.TransInner.classOfType(TransInner.java:1582)
at com.sun.tools.javac.v8.comp.TransInner.classOf(TransInner.java:1547)
at com.sun.tools.javac.v8.comp.TransInner._case(TransInner.java:1954)
at com.sun.tools.javac.v8.tree.Tree$Select.visit(Tree.java:1200)
at com.sun.tools.javac.v8.tree.TreeTranslator.translate(TreeTranslator.java:45)
at com.sun.tools.javac.v8.tree.TreeTranslator._case(TreeTranslator.java:120)
at com.sun.tools.javac.v8.tree.Tree$VarDef.visit(Tree.java:604)
at com.sun.tools.javac.v8.tree.TreeTranslator.translate(TreeTranslator.java:45)
at com.sun.tools.javac.v8.tree.TreeTranslator.translate(TreeTranslator.java:58)
at com.sun.tools.javac.v8.tree.TreeTranslator._case(TreeTranslator.java:129)
at com.sun.tools.javac.v8.tree.Tree$Block.visit(Tree.java:644)
at com.sun.tools.javac.v8.tree.TreeTranslator.translate(TreeTranslator.java:45)
at com.sun.tools.javac.v8.tree.TreeTranslator._case(TreeTranslator.java:114)
at com.sun.tools.javac.v8.comp.TransInner._case(TransInner.java:1748)
at com.sun.tools.javac.v8.tree.Tree$MethodDef.visit(Tree.java:569)
at com.sun.tools.javac.v8.tree.TreeTranslator.translate(TreeTranslator.java:45)
at com.sun.tools.javac.v8.comp.TransInner._case(TransInner.java:1678)
at com.sun.tools.javac.v8.tree.Tree$ClassDef.visit(Tree.java:521)
at com.sun.tools.javac.v8.tree.TreeTranslator.translate(TreeTranslator.java:45)
at com.sun.tools.javac.v8.comp.TransInner.translate(TransInner.java:1638)
at com.sun.tools.javac.v8.comp.TransInner.translateTopLevelClass(TransInner.java:1988)
at com.sun.tools.javac.v8.JavaCompiler.compile(JavaCompiler.java:484)
at com.sun.tools.javac.v8.Main.compile(Main.java:505)
at com.sun.tools.javac.Main.compile(Main.java:27)
at com.sun.tools.javac.Main.main(Main.java:16)
-------------------------------------------------------------------------------
On the other hand, using other internally used names such as 'this$n', compiler
gives proper error message.
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