How to detect C++ loop block after parsing the code using antlr4?

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I am working with Antlr4 and I want to parse and analyze any c++ code to detect any loops in any c++ source code to do dependency analysis on them, but I can't detect any loop in the source code.

What I have tried:

This is the rule that I used for "for loops" in Antlr:

forBlock: 'for' '(' (classicFor | forEach) ')' controlStructureBody ;
forExpression: primaryExpression (',' primaryExpression)* ;

I print out the tokens in this code:

C++

<pre>#include <iostream>
using namespace std;
int main()
{
    for (int i = 0; i <= 5; i++) {
        for (int j = 0; j <= 5; j++) {
            cout << i << j << " \t";
        }
        cout << "\n";
    }
    return 0;
}

using this code:

Java

public void printToken(String inputFile) throws FileNotFoundException, IOException {
        System.out.println("The tokens of the source code is: \n");
        CharStream inputStream = CharStreams.fromFileName(inputFile);
        TokensLexer tokensLexer = new TokensLexer(inputStream);
        CommonTokenStream tokenStream = new CommonTokenStream(tokensLexer);
        tokenStream.fill();
        for (Token token : tokenStream.getTokens()) {
            System.out.println("<" + token.getText() + "> " + "<" + token.getType() + ">");
        }
    }

and it gave me the type of each for loop as

<for> <45>

<for> <45>

I tried this code:

Java

        CharStream inputStream = CharStreams.fromFileName(inputFile);
        // lexing the code
        TokensLexer tokensLexer = new TokensLexer(inputStream);
        CommonTokenStream tokenStream = new CommonTokenStream(tokensLexer);
        // parsing the code
        TokensParser tokensParser = new TokensParser(tokenStream);
        tokenStream.fill();
        for (Token token : tokenStream.getTokens()) {
            if (token.getType() == 45)
                System.out.println("loop is found");
        }
}

When I put "45" it prints out loop is found twice and when I change the number to "39" it prints out loop is found only one.

I tried "39" because I have this value in my generated files from Antlr grammar.
Tokens.tokens -> for = 45.
Tokens.lexer.tokens -> for = 45.
TokensParser.java -> Rule_forBlock = 39; Rule_forExpression = 40;

and when I try to add more loops:

C++

#include <iostream>
using namespace std;
int main()
{
    for (int i = 0; i <= 5; i++) 
    {
        for (int j = 0; j <= 5; j++) {
            cout << i << j << " \t";
        }
        cout << "\n";
    }
    for (int  i = 0; i < 100; i++)
    {
       cout<<"Test"<<endl;
    }
    
    return 0;
}

and use the number 39 still detects only one loop.

Is there a way to detect the loops in the source code using Antlr and differentiate between the outer and inner loop?

Posted 22-Aug-20 11:09am

HishamMohammedA

Updated 25-Sep-20 12:08pm

v4

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Stefan_Lang 25-Aug-20 11:57am

I have no idea about Antlr or how it works. But the grammer you defined doesn't distinguish between a for loop body consisting of a single statement ending in ';', or a code block enclosed in '{' and '}' which may not end in ';'. Specifically your last code example has multiple for loops not ending in ';'

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Jiri111 · Answer 1 · 2020-09-25T12:08:00

Solution 1

Why don't you post the whole grammar? This is just a fraction of it. In you examples, it shall enter the "classicFor". How is this classicFor defined?

The output indicates that you code just recognized the "for" token.

Posted 25-Sep-20 12:08pm

Jiri111

Comments

HishamMohammedA 6-Oct-20 14:20pm

okay, I was able to locate for loop but now I have a problem of recognizing the nested loop when I use visitor.

I am using this peace of grammar,
iterationstatement
: While '(' condition ')' statement #WhileStatement
| Do statement While '(' expression ')' ';' #DoWhileStatemen
| For '(' forinitstatement condition? ';' expression? ')' statement #ClassicForStatement
;
to visit for loop and write above it, after doing some analysis on the string forStr.

public T visitClassicForStatement(GrammarParser.ClassicForStatementContext ctx) {
String forStr =ctx.statement().compoundstatement().statementseq().statement().getText();

this string supposes to be statements inside the for loop, but I am facing a problem that when I put nested loop and when I receive this text I receive the for loop with it.
the problem is:
when I am receiving a statement like this:
for(){statements}
my analysis work on statements just fine but when I receive it like this:
for(){for(){statments}}
I have a problem because the inner loop comes with statements and this makes a problem for my way to analyze.

How I can ignore the inner for loop and take only statements like the way I take it when I have only a single loop, and write only above the outer loop.

this is the grammar that I use:
https://gofile.io/d/CLRikA