Hello,
I used ANTLR v3.2 and ANTLRWorks v1.4 to build multiple small tools. Recently I
encountered the problem, that a rather trivial grammar causes IMHO
inappropriately high runtime and memory usage.
Looking for my mistake, I stripped the grammar down to following one:
----------------------------------------------------------------------------------------------------------------------------------------
grammar problem;
main_rule
: SOMETOKEN;
SOMETOKEN
: ('a')*;
----------------------------------------------------------------------------------------------------------------------------------------
>From this source file I compiled a grammar using ANTLRWorks v1.4 and
>surrounded it with the standard Java code from the TDAR (so nothing special
>here).
If I feed the parser some input, that is not valid with respect to the above
grammar (it can be anything, take e.g. the following string of only one
character: "<"), it will take a lot of processor time and consume very high
amounts of memory. E.g. I configured a limit of 1 GB of RAM in Eclipse (using
"-Xmx1024m") and it's taking this amount.
To be complete, I also list the code calling the parser here:
----------------------------------------------------------------------------------------------------------------------------------------
public static void main(String[] args) throws Exception
{
ANTLRStringStream input = new ANTLRStringStream("<");
problemLexer lexer = new problemLexer(input);
CommonTokenStream tokens = new CommonTokenStream(lexer);
problemParser parser = new problemParser(tokens);
parser.main_rule();
}
----------------------------------------------------------------------------------------------------------------------------------------
=> Did I make some beginner's error and I'm just not able to see it?
Thanks in advance and best regards,
Ralf Cremerius
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