Question

How do i parse multiple source file and end up with just one AST to perform analysis and code generation from? Typically, I find example usage of ANTLR in the form of

public void process(String source) 
{
    ANTLRStringStream Input = new ANTLRStringStream(input);
    TLexer lex = new TLexer(Input);
    CommonTokenStream tokens = new CommonTokenStream(lex);
    TParser parser = new TParser(tokens);
    var tree = parser.parse().Tree; 
} 

but neither the lexer nor the parser seems to be able to take additional files. Am I supposed to create a lexer and parser pr. inputfile and use tree.Add() to add trees from the other files to the tree of the first file?

Answer 1

Here are three ways you could do this:

1. Use Bart’s suggestion and combine the files into a single buffer. This would require adding a lexer rule that implements identical functionality to the C++ #line directive.

2. Combine the trees returned by the parser rule.

3. Use multiple input streams with a single lexer. This can be done by using code similar to that which handles include files by pushing all buffers onto the stack before lexing.

The second option would probably be the easiest. I don’t use the Java target so I can’t give code details, which is required for all of these solutions.