Illegal field name when trying to compile with a javax.swing.Action
David Alayachew
davidalayachew at gmail.com
Mon Aug 7 19:17:07 UTC 2023
Hello Rémi,
Thank you for your response!
And thanks for checking. I had tried to debug this issue earlier on, but
couldn't quite pin down the source.
I am completely ignorant about the LocalVariableTable, so I can't respond
to that or the spec stuff.
If there is any info I can provide, please let me know.
Thank you for your time and help!
David Alayachew
On Mon, Aug 7, 2023 at 3:10 PM Remi Forax <forax at univ-mlv.fr> wrote:
> Hi David,
> thanks for the bug report.
>
> I was able to reproduce the issue with the latest early acces of 22,
> There is no issue if "-g" is not specified, so the bug seems to be in the
> debug information that are added to the classfile.
>
> javac -g --enable-preview --source 22 GUI.java
>
> Here is a simpler reproducer
>
>
> import java.util.function.Consumer;
>
> public class GUI {
> public static void main(String[] args) {
> Consumer<String> op = _ -> {};
> }
> }
>
>
> javap shows the issue, the LocalVariableTable is generated with the name ""
>
> private static void lambda$main$0(java.lang.String);
> descriptor: (Ljava/lang/String;)V
> flags: (0x100a) ACC_PRIVATE, ACC_STATIC, ACC_SYNTHETIC
> Code:
> stack=0, locals=1, args_size=1
> 0: return
> LineNumberTable:
> line 5: 0
> LocalVariableTable:
> Start Length Slot Name Signature
> 0 1 0 Ljava/lang/String;
>
> The JVM spec 4.7.13 said
> "
> name_index
>
> The value of the name_index item must be a valid index into the
> constant_pool table. The constant_pool entry at that index must contain a
> CONSTANT_Utf8_info structure representing a valid unqualified name
> denoting a local variable (§4.2.2
> <https://docs.oracle.com/javase/specs/jvms/se20/html/jvms-4.html#jvms-4.2.2>
> ).
>
> "
>
> And 4.2.2 said that the string must have at least one code point, so "" is
> an invalid name, rightly rejected by the VM (the error message is just not
> great, it's not about a field but a local variable name, here a parameter
> inside the LocalVariableTable).
>
> So it's a bug in the compiler, I see two ways to fix it, either do not
> generate a line in the LocalVariableTable if the parameter is unamed or use
> "_" instead.
>
> regards,
> Rémi
>
> ------------------------------
>
> *From: *"David Alayachew" <davidalayachew at gmail.com>
> *To: *"amber-dev" <amber-dev at openjdk.org>
> *Sent: *Sunday, August 6, 2023 4:31:54 PM
> *Subject: *Re: Illegal field name when trying to compile with a
> javax.swing.Action
>
> Also, here is my version info.
>
>
> $ java --version
> openjdk 21-ea 2023-09-19
> OpenJDK Runtime Environment (build 21-ea+31-2444)
> OpenJDK 64-Bit Server VM (build 21-ea+31-2444, mixed mode, sharing)
>
>
> $ javac --version
> javac 21-ea
>
>
>
> On Sun, Aug 6, 2023 at 7:31 PM David Alayachew <davidalayachew at gmail.com>
> wrote:
>
>> Hello Amber Dev Team,
>>
>> I ran into a problem that I am not sure what the cause is. It only seems
>> to occur when I am using unnamed variables.
>>
>>
>> Here are the commands that I am using, as well as their outputs.
>>
>>
>> $ javac -g -Xlint:all,-preview,-serial -Xdiags:verbose --enable-preview
>> --source 21 GUI.java
>> Note: GUI.java uses preview features of Java SE 21.
>> Note: Recompile with -Xlint:preview for details.
>>
>>
>> $ java --enable-preview GUI
>> Error: LinkageError occurred while loading main class GUI
>> java.lang.ClassFormatError: Illegal field name "" in class GUI
>>
>> And here is the file that I am using.
>>
>>
>> import javax.swing.JPanel;
>> import javax.swing.JLabel;
>> import javax.swing.JButton;
>> import java.util.function.BiFunction;
>>
>> public class GUI
>> {
>>
>> public static void main(String[] args)
>> {
>>
>> new GUI(null, null);
>>
>> }
>>
>> public GUI(final Object characterType, final Object icon)
>> {
>>
>> }
>>
>> private Object createConstraintPanel()
>> {
>>
>> final JPanel constraintPanel = new JPanel();
>> final JButton button = new JButton();
>>
>> CREATE_INPUT_SANITIZATION:
>> {
>>
>> BUTTON_ACTION_LISTENER:
>> {
>>
>> button
>> .addActionListener
>> (
>> _ ->
>> {
>>
>> final BiFunction<String, Integer, JLabel>
>> createLabel =
>> (text, width) ->
>> {
>>
>> return null;
>>
>> }
>> ;
>>
>> final JButton remove = new JButton();
>> remove
>> .addActionListener
>> (
>> _ ->
>> {
>>
>>
>> }
>> );
>>
>> }
>> )
>> ;
>>
>> }
>>
>> }
>>
>> return constraintPanel;
>>
>> }
>>
>> }
>>
>> Technically, this issue also occurs if even 1 of the 2 unnamed variables
>> is turned into a real variable. But regardless, the point is, this fails at
>> run time.
>>
>> Please let me know if there is anything I am missing.
>>
>> Thank you for your time and help!
>> David Alayachew
>>
>>
>> On Tue, Jul 18, 2023 at 1:54 AM David Alayachew <davidalayachew at gmail.com>
>> wrote:
>>
>>> Ok, ty for the heads up.
>>>
>>> On Tue, Jul 18, 2023 at 1:18 AM - <liangchenblue at gmail.com> wrote:
>>>
>>>> Hi David,
>>>> Please do not ask for technical support in the development mailing
>>>> list. There's no proof that this issue is with the core libraries instead
>>>> of the Java compiler or another component.
>>>> I have already downloaded your zip, compiled the 4 files with JDK 22
>>>> (my local dev build for another unrelated patch) javac --enable-preview
>>>> -release 22 *.java and java --enable-preview ToDoList, which just shows up
>>>> a UI without any crash. Without enable-preview, yoru code does not compile
>>>> at all for the usage of _ as an identifier.
>>>>
>>>> This is most likely a problem with the compiler you are using; you have
>>>> a gpj file, which probably means you are using jGrasp. Please report this
>>>> issue to the relevant parties (i.e. the 3rd-party IDE or whatever supports
>>>> using _ as identifer without --enable-preview) instead.
>>>>
>>>> Chen Liang
>>>>
>>>> On Tue, Jul 18, 2023 at 11:43 AM David Alayachew <
>>>> davidalayachew at gmail.com> wrote:
>>>>
>>>>> Wait, nevermind. Don't ignore. I was able to recreate this issue on
>>>>> the command line using the abovementioned JDK. Could someone come back and
>>>>> take a look at this please?
>>>>>
>>>>> Sorry for jerking everyone around here. I have multiple JDK's and got
>>>>> mixed up on which one I was using.
>>>>>
>>>>> On Sun, Jul 16, 2023 at 2:26 AM David Alayachew <
>>>>> davidalayachew at gmail.com> wrote:
>>>>>
>>>>>> Hmmmm, this one might actually be IDE specific. Please ignore.
>>>>>>
>>>>>
>
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