使用ANTLR来获取标识符和函数名

问题描述

我试图使用和理解ANTLR，这是新的我。我的目的是读取C语言编写的源$ C ​​$ C文件，并从中提取标识符（变量和函数名）。

I'm trying to use and understand AntLR, this is new to me. My purpose is to read a source code file written in C and extract from it the identifiers (variables and function names).

在我的C语法（文件的 C.g4 ）认为：

In my C grammar (file C.g4) consider:

identifierList
    :   Identifier
    |   identifierList Comma Identifier
    ;
Identifier
    :   IdentifierNondigit
        (   IdentifierNondigit
        |   Digit
        )*
    ;

在代解析器和听众的创建我自己的监听器标识符列表。

After generation of parser and listener I create my own listener to the identifierList.

注意MyCListener类扩展CBaseListener：

Note that MyCListener class extends CBaseListener:

public class MyCListener extends CBaseListener {


@Override
public void enterIdentifierList(CParser.IdentifierListContext ctx) {
    List<ParseTree> children = ctx.children;
    for (ParseTree parseTree : children) {
        System.out.println(parseTree.getText());
    }

}

然后，我有这个在主类：

Then I have this in main class:

 String fileurl = "C:/example.c";

 CLexer lexer;
 try {
       lexer = new CLexer(new ANTLRFileStream(fileurl));
       CommonTokenStream tokens = new CommonTokenStream(lexer);
       CParser parser = new CParser(tokens);

       CParser.IdentifierListContext identifierContext = parser.identifierList();
       ParseTreeWalker walker = new ParseTreeWalker();
       MyCListener listener = new MyCListener();
       walker.walk(listener, identifierContext);

 } catch (IOException ex) {
       Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);
 }

在哪里example.c是：

Where example.c is:

int main() {

// this is C

 int i=0; // i is int
 /* double j=0.0;
    C
 */
}

我是什么做错了吗？
也许我没有写正确MyCListener或标识符列表是不是我需要听......真的不知道。我很抱歉，但我甚至不知道我的输出，为什么会出现词法错误：

What am I doing wrong?Maybe I didn't write MyCListener properly, or identifierList is not what I need to listen... Really don't know. I'm sorry, but I didn't even understand my output, why is there a lexical error?:

line 3:4 mismatched input '(' expecting {<EOF>, ','}
main
(
)
{
int
i
=
0
;
}

正如你所见，我对此很困惑。有人可以帮我吗？请...

As you see, I'm very confused about this. Can somebody help me ? Please...

推荐答案

通过这一行：

CParser.IdentifierListContext identifierContext = parser.identifierList();

你试图解析您的整个输入作为标识符列表。但是你的输入不只是这一点。

you're trying to parse your entire input as an identifierList. But your input isn't just that.

假设你正在使用的，尽量让在语法（这是规则的切入点解析器启动 compilationUnit ）

Assuming you're using the C.g4 from the ANTLR4 Github repository, try to let the parser start at the entry point of the grammar (which is the rule compilationUnit):

MyCListener listener = new MyCListener();
ParseTreeWalker.DEFAULT.walk(listener, parser.compilationUnit());

修改

下面是一个简单的演示：

EDIT

Here's a quick demo:

public class Main {

    public static void main(String[] args) throws Exception {

        final List<String> identifiers = new ArrayList<String>();

        String source = "int main() {\n" +
                "\n" +
                "// this is C\n" +
                "\n" +
                " int i=0; // i is int\n" +
                " /* double j=0.0;\n" +
                "    C\n" +
                " */\n" +
                "}";

        CLexer lexer = new CLexer(new ANTLRInputStream(source));
        CParser parser = new CParser(new CommonTokenStream(lexer));

        ParseTreeWalker.DEFAULT.walk(new CBaseListener(){

            @Override
            public void enterDirectDeclarator(@NotNull CParser.DirectDeclaratorContext ctx) {
                if (ctx.Identifier() != null) {
                    identifiers.add(ctx.Identifier().getText());
                }
            }

            // Perhaps override other rules that use `Identifier`

        }, parser.compilationUnit());

        System.out.println("identifiers -> " + identifiers);
    }
}

这将打印：

identifiers -> [main, i]

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