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Date: Sat, 26 Feb 2005 16:13:00 -0000
From: "bonniot at users dot sf dot net" <gcc-bugzilla@gcc.gnu.org>
To: java-prs@gcc.gnu.org
Message-ID: <20050225194856.20215.bonniot@users.sf.net>
Reply-To: gcc-bugzilla@gcc.gnu.org
Subject: [Bug java/20215] New: gcj does not accept classes with same name fields
X-Bugzilla-Reason: CC
X-SW-Source: 2005-q1/txt/msg00531.txt.bz2
List-Id: <java-prs.sourceware.org>

According to the JVM spec, class files can have several fields with the same
name. As long as they have different types, they will be distinguished since all
field operations specify both the name and the field of the field. Sun's JVM
accepts such classes, and correctly distinguishes the fields, as you can see in
the attached testcase. Here is the disassembly of this class:

Access flags: 0x20 super
This class: 2=DuplicateField, super: 4=java.lang.Object
Interfaces (count: 0):

Fields (count: 2):
Field name:"foo" static Signature: 6=java.lang.String
Field name:"foo" static Signature: 7=int

Methods (count: 3):

Method name:"<init>" Signature: 9=()void
Attribute "Code", length:17, max_stack:1, max_locals:1, code_length:5
  0: aload_0
  1: invokespecial #11=<Method java.lang.Object.<init> ()void>
  4: return

Method name:"main" public static Signature: 14=(java.lang.String[])void
Attribute "Code", length:31, max_stack:2, max_locals:1, code_length:19
  0: getstatic #20=<Field java.lang.System.out java.io.PrintStream>
  3: getstatic #22=<Field DuplicateField.foo java.lang.String>
  6: invokevirtual #28=<Method java.io.PrintStream.println (java.lang.String)void>
  9: getstatic #20=<Field java.lang.System.out java.io.PrintStream>
 12: getstatic #30=<Field DuplicateField.foo int>
 15: invokevirtual #33=<Method java.io.PrintStream.println (int)void>
 18: return

Method name:"<clinit>" static Signature: 9=()void
Attribute "Code", length:24, max_stack:1, max_locals:0, code_length:12
  0: ldc #36=<String "WOW">
  2: putstatic #22=<Field DuplicateField.foo java.lang.String>
  5: sipush 42
  8: putstatic #30=<Field DuplicateField.foo int>
 11: return


Sun's JVM correctly executes that program:

$ java DuplicateField
WOW
42

gcj fails during compilation with:

$ gcj DuplicateField.class
DuplicateField.java: In class 'DuplicateField':
DuplicateField.java: In method 'DuplicateField.main(java.lang.String[])':
DuplicateField.java:0: error: mismatching signature for field 'foo' in
'DuplicateField'
DuplicateField.java: In method 'DuplicateField.<clinit>()':
DuplicateField.java:0: error: mismatching signature for field 'foo' in
'DuplicateField'

Surprisingly, gij also fails with:

Exception in thread "main" java.lang.NullPointerException
   at java.io.PrintStream.println(java.lang.String) (/tmp/gcc/lib/libgcj.so.6.0.0)
   at DuplicateField.main(java.lang.String[]) (Unknown Source)
   at gnu.java.lang.MainThread.call_main() (/tmp/gcc/lib/libgcj.so.6.0.0)
   at gnu.java.lang.MainThread.run() (/tmp/gcc/lib/libgcj.so.6.0.0)

gcj (GCC) 4.0.0 20050223

-- 
           Summary: gcj does not accept classes with same name fields
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: java
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: bonniot at users dot sf dot net
                CC: gcc-bugs at gcc dot gnu dot org,java-prs at gcc dot gnu
                    dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20215