[antlr-interest] Can I target C and Java from one grammar file?

[Johannes Luber]

Jim Idle schrieb:
> Andy Grove wrote:
>> Hi,
>>
>> I need to generate C and Java from an ANTLR grammar containing  
>> actions. Is there a preprocessor approach I can use rather than  
>> maintaining two versions of the grammar?
>>   
> I use perforce and maintain a base grammar that has no actions, then 
> change only the grammar base. When ready to test I integrate the changes 
> via a prestored branch spec. Other SCCS can do the same sort of thing, 
> though perforce is streets ahead of anything else at the merge process.
> 
> However, occasionally it is a pain to debug remotely when I want to just 
> use the ANTLR works debugger before integrating a change, so I have 
> written a pre-processor as an experiment (it is in ANTLR3 of course), 
> and am trying to decide between the C# lexer base approach and the VB/C 
> approach (albeit not having the stupidity of the VB pre-processor.)

Having a preprocessor would allow me to have a single grammar for C#,
while allowing to serve it my own needs and the general ones at once.
I've thought about using C#'s preprocessor, but that would at best allow
to circumvent the assignments, but not any initializations.
> 
> I was then going to propose it to Ter as an addon for the next release 
> (as it is non invasive if you don't use any pre-processing instructions.
> 
> Then you can have:
> 
> options
> {
>    #if TARGET="C"
>        language = C;
>    #else
>        language = Java;
>    #endif
> }
> 
> Or perhaps
> 
>   language  =  TARGET_LANG;
> 
> and, referencing a prior thread:
> 
> #ifdef ANTLR_VER_MAJOR > 3 || ANTLR_VER_MINOR < 2
> #abort "This grammar requires ANTLR 3.1.2 and above"
> #endif
> 
> If I am willing to do the C macro thing. In general though, if you add 
> macros, people start embedding code in them and the whole thing is 
> macros, so I prefer the minimalist approach of C#.

Instead doing it with macros,how about using:

#ifdef ANTLR_3_1_2

and let ANTLR defines this symbol, as long it remains backwards
compatible (ignoring bugfixes here).
> 
> As far as code generation goes, and maybe this would solve 
> preprocessing, I think it would be good to be able to supply a string 
> template for action code generation (rather than for the parser to use 
> at runtime). So you would have:
> 
> language = template;
> 
> r1 : %r1predicate(x)%?=>   a=INT bINT c=INT 

Can you explain this in more detail? I'm not sure how you arrive at
those and what the purpose actually is.
> 
> For now though, m4 is your best bet (it is in the Java compiler even), 
> or perhaps something simple with gawk.

What is m4? I find only weapon references.

Johannes
> 
> Jim
>> I'm thinking that the grammar would look something like this:
>>
>> selectStatement[int initRule]
>> //IFDEF JAVA
>> @init 	{if(initRule) sse.pushCall(sse.SELECTSTAT);}
>> //ELIFDEF CPP
>> @init 	{if(initRule) sse->pushCall(sse.SELECTSTAT);}
>> //END
>> 	:
>> 	q = queryExpression[true]
>> 	;
>>
>> Are there tools out there already or do I need to roll my own?
>>
>> Thanks,
>>
>> Andy Grove
>> Chief Architect
>> CodeFutures Corporation
>>
>>
>>
>>
>>
>>
>>
>>
>>
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> 
> 
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