title: How to fix breakpoint error when debugging in Eclipse?
body: <p>Need to debug a JAR file "ProA", so import the source code in the project,
  but there is a strange error in Eclipse while trying to set a breakpoint.
  Detail as below:</p>
  
  <pre><code>Unable to install breakpoint due to missing line number attributes.
  Modify compiler options to generate line number attributes.
  </code></pre>
  
  <p>I have try to several method to solve, but failed.</p>
  
  <ol>
  <li>Under <em>Window > Preferences: Java > Compiler > Classfile Generation</em>, all options have to be to True</li>
  <li>In <code>.settings</code> folder of your project, look for a file called <code>org.eclipse.jdt.core.prefs</code>. Verify or set <code>org.eclipse.jdt.core.compiler.debug.lineNumber=generate</code></li>
  <li>Add the <code>debug=true</code> flag in the <code>build.xml</code>, just like this: <code>&lt;javac srcdir="./src/java" destdir="./bin" debug="true"&gt;</code></li>
  </ol>
  
  <p>Any help will be appreciated. </p>