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I want to add some code to the C source code, so I try to use ASTRewrite.
My Github project: cdt-rewrite
My code:

enter image description here

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;

import org.eclipse.cdt.core.dom.ast.ASTVisitor;
import org.eclipse.cdt.core.dom.ast.IASTIfStatement;
import org.eclipse.cdt.core.dom.ast.IASTStatement;
import org.eclipse.cdt.core.dom.ast.IASTTranslationUnit;
import org.eclipse.cdt.core.dom.ast.gnu.c.GCCLanguage;
import org.eclipse.cdt.core.dom.rewrite.ASTRewrite;
import org.eclipse.cdt.core.model.ILanguage;
import org.eclipse.cdt.core.parser.DefaultLogService;
import org.eclipse.cdt.core.parser.FileContent;
import org.eclipse.cdt.core.parser.IncludeFileContentProvider;
import org.eclipse.cdt.core.parser.ScannerInfo;
import org.eclipse.core.runtime.NullProgressMonitor;
import org.eclipse.ltk.core.refactoring.Change;


public class Main {

    public static void main(String[] args) throws Exception {
        IASTTranslationUnit u = getTranslationUnit(new File("D:/test.c"));
        System.out.println(u.getRawSignature());

        ASTRewrite rw = ASTRewrite.create(u);
        u.accept(new ASTVisitor(true) {

            @Override
            public int visit(IASTStatement stm) {

                if (stm instanceof IASTIfStatement){
                    rw.insertBefore(stm.getParent(), stm, 
                            rw.createLiteralNode("callTo(1,2,3);"), null);
                }

                return PROCESS_CONTINUE;
            }

        });

        Change c = rw.rewriteAST();
        c.perform(new NullProgressMonitor());
        //String changedSource = someHowGetCode(c);
    }

    static IASTTranslationUnit getTranslationUnit(File source) throws Exception{
        FileContent reader = FileContent.create(
                source.getAbsolutePath(), 
                getContentFile(source).toCharArray());

        return GCCLanguage.getDefault().getASTTranslationUnit(
                reader, 
                new ScannerInfo(), 
                IncludeFileContentProvider.getSavedFilesProvider(), 
                null, 
                ILanguage.OPTION_IS_SOURCE_UNIT, 
                new DefaultLogService());
    }

    static String getContentFile(File file) throws IOException {
        StringBuilder content = new StringBuilder();
        String line;

        try (BufferedReader br = new BufferedReader(
                new InputStreamReader(new FileInputStream(file)))) {
            while ((line = br.readLine()) != null)
                content.append(line).append('\n');
        }

        return content.toString();
    }
}

But when I run this code, an exception is occur:

int test(int x){
    if (x < 0)
        return 0;
    int i, s = 0;
    for (i = 1; i < x; i++)
        s = s + i;
    return s;
}

Exception in thread "main" java.lang.NullPointerException
    at org.eclipse.cdt.internal.formatter.ChangeFormatter.formatChangedCode(ChangeFormatter.java:92)
    at org.eclipse.cdt.internal.core.dom.rewrite.changegenerator.ChangeGenerator.generateChange(ChangeGenerator.java:117)
    at org.eclipse.cdt.internal.core.dom.rewrite.changegenerator.ChangeGenerator.generateChange(ChangeGenerator.java:104)
    at org.eclipse.cdt.internal.core.dom.rewrite.ASTRewriteAnalyzer.rewriteAST(ASTRewriteAnalyzer.java:26)
    at org.eclipse.cdt.core.dom.rewrite.ASTRewrite.rewriteAST(ASTRewrite.java:212)
    at Main.main(Main.java:44)

Does anyone know how to solve this exception?
Thanks you

phibao37
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1 Answers1

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AFAIK This code is dependent on running in OSGi, but you appear to have made a Java project with a main. You need to a plug-in project with a MANIFEST.MF that references what you require.

You can create an Eclipse Application if you want to control the entry point to the program. If you want to graduate this rewriting code to be part of Eclipse/CDT, then different entry points such as an Eclipse Command tied to a menu/toolbar/key combination may be what you want.

Jonah Graham
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  • I am developing a plugin and also try to rewrite c code using the eclipse c ast parser. I getting the same NPE as mentionen in the question. Do you have any further advice? @Jonah Graham – ag00se May 04 '21 at 07:58
  • Nothing new to add - if you are trying to use it outside like the OP then my answer still stands AFAIK. If you are using in OSGi, then you have a new question - which you seem to have asked and answered here: https://stackoverflow.com/a/67398617/2796832. Glad you solved your issue. – Jonah Graham May 21 '21 at 12:52