Re: [PATCH 3/4] java: add support for lookahead correction

Interesting…. Good that there was a test case for that! :)

From: Akim Demaille <[email protected]>
Date: Wednesday, 4. November 2020 at 07:17
To: Akim Demaille <[email protected]>
Cc: Adrian Vogelsgesang <[email protected]>, "[email protected]" <[email protected]>
Subject: Re: [PATCH 3/4] java: add support for lookahead correction

Hi Adrian,

> Le 2 nov. 2020 à 07:32, Akim Demaille <[email protected]> a écrit :
>
>> Le 2 nov. 2020 à 01:50, Adrian Vogelsgesang <[email protected]> a écrit :
>>
>> public ]b4_parser_class[(]b4_parse_param_decl([b4_lex_param_decl])[)]b4_maybe_throws([b4_init_throws])[
>> {
>> -]b4_percent_code_get([[init]])[
>> - this.yylexer = new YYLexer (]b4_lex_param_call[);
>> +]b4_percent_code_get([[init]])[]b4_lac_if([[
>> + this.yylacStack = new Vector<Integer>();
>> + this.yylacEstablished = false;]])[
>> + this.yylexer = new YYLexer(]b4_lex_param_call[);
>> ]b4_parse_param_cons[
>>
>>
>> Why do we place the user-provided init-code first?
>> Does that mean, the user must not call any methoes which might depend on `yylexer`?
>> Not sure if this actually matters, but I would put the user-provided init-code last, so that the rest of the class is already initialized…
>
> It makes sense, I'll change that. Thanks!

Well, it turns out that this was by design, to be able to call 'super'.
When I tried that change, the test suite failed:

> http://YYParser.java:294<http://YYParser.java:294> error: call to super must be first statement in constructor
> super("Test Thread"); if (true) throw new InterruptedException();
> ^


That's test 682, http://java.at:470<http://java.at:470>, Java constructor init and init_throws:

> m4_pushdef([AT_Witness],
> [super("Test Thread"); if (true) throw new InterruptedException();])
>
> AT_CHECK_JAVA_MINIMAL([[
> %define extends {Thread}
> %code init { ]AT_Witness[ }
> %define init_throws {InterruptedException}
> %lex-param {int lex_param}]])
> AT_CHECK([[grep ']AT_Witness[' YYParser.java]], 0, [ignore])

And it's documented:

> Use @code{%code init} for code added to the start of the constructor
> body. This is especially useful to initialize superclasses. Use
> @samp{%define init_throws} to specify any uncaught exceptions.


Cheers!