Skip to main content
Jump to: navigation, search



Code Formatting

  • It is recommended to preserve formatting and style of old code when making patches
  • It is recommended to use default "Eclipse" code formatting for Java for new code (which is 120 chars line width for code and 80 for comments)
    • Note: Please don't rely completely on Java auto-formatter that is known to be buggy (see bug 303519).
  • It is recommended to use code blocks (curly brackets) for for/while/do/if statement bodies, with the exception of simple terminating statements, i.e. "if (a) return;"
  • It is strongly recommended to use Organize Imports action on save

Eclipse Java Errors/Warnings

It is strongly recommended for cdt plugins to override default compiler error/warning and use project specific errors/warnings. Projects should have the following customizations:

  • Method with a constructor name - Error
  • Assignment has no effect - Error
  • Possible accidental boolean assignment - Error
  • finally does not complete normally - Error
  • Using a char array in string concatenation - Error
  • Null pointer access - Error
  • Potential null pointer access - Warning
  • Unused Import - Error

All commiters and contributors submitting patches should enable API tooling by setting target baseline platform. Do not commit code with API errors.

Patches with errors listed above including API errors will not be accepted without corrections.

Committers who wish to keep a plugin warning-free should update the project as follows. These steps turns warnings into errors and leaves everything else in the ignore state. In other words, the idea is not to turn everything into an error, just the things that are set to generate a warning.

  1. Open project properties > Java Compiler > Errors/Warnings
    1. Turn on Enable project specific settings
    2. Turn on Annotations > Suppress optional errors with '@SuppressWarnings' (new pref in Helios)
  2. Open .setings/org.eclipse.jdt.core.prefs in a text editor and do a find&replace of "=warning" to "=error" (use Replace All)
  3. Turn on project properties > Plug-in Development > API Errors/Warnings > Use project settings
  4. Open .settings/ in a text editor and do a find&replace of "=Warning" to "=Error" (use Replace All; 'W' and 'E' must be uppercase)
  5. Turn on project properties > Plug-in Development > Plug-in Manifest Compiler > Use project settings
  6. Open .settings/org.eclipse.pde.prefs in a text editor and do a find&replace of "=1" to "=0" (use Replace All)


Use eclipse copyright header: Here is an example:

 * Copyright (c) {date} {owner}[ and others]
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License 2.0 which is available at
 * SPDX-License-Identifier: EPL-2.0
 * Contributors:
 *   {name} - initial API and implementation

A contributors line can be added for significant changes in the file but this is optional.


There are 3 types of API: Public API, Provisional API and Internal API (aka Private API, aka non API). Public API is what all client should use, it suppose to be documented (javadoc) and should not change much from version to version. If major version of the plugin changed it may contain API breakage. If minor version of the plugin changed it may contain API extensions (non-breaking changes). There is also some policies about changing API between milestone builds. Provisional API is a public API in making. It does not have to follow versioning and other rules of public API, but other than that, it can be threated as public.

Examples API breaking change:

  • Adding a method in interface
  • Changing method signature
  • Changing private visibility to any other

Examples of API extensions:

  • Adding new extension point
  • Changing visibility from protected to public
  • Adding method in a class

So here is what considered Internal API vs Public vs Provisional for CDT

  • Internal API
    • packages with name *.internal.*, *.examples.*
    • test projects, releng projects and feature projects
    • packages which are not exported or X-exported (i.e. not exported as public)
    • non-java code (i.e. native C code)
    • private and package private classes and members
  • Provisional API
    • packages with names *.provisional*
    • class that are marked EXPERIMENTAL and all its members
 EXPERIMENTAL. This class or interface has been added as part
 of a work in progress. There is no guarantee that this API will work or that
 it will remain the same.
  • Public API
    • everything which is not internal or provisional and
      • has public or protected java visibility
      • in public exported package
    • public API class or interface can also have some usage exceptions:
      • classes and members marked @noreference in the javadoc comment cannot be used and not considered public API even if they have public visibility
      • classes and interfaces that are marked as @noextend should not be extended
      • interfaces that are marked @noimplement should not be implemented

See also Evolving Java-based APIs.

Note: you can still use internal API is you want to, if java visibility allows you (even if it does not, you can hack it, using reflection). The only problem with this approach is that internal API can be changed without notice or trace, so you would have hard time making your code compile or run with new version of the tool. The best approach in this case to submit a bug asking to create an API for functionality you are looking for.

Using API Tooling

All committers and contributors should enable API Tooling when writing patches for CDT.

Using Eclipse 4.5.0 and greater

Starting with Eclipse 4.5.0, it is no longer necessary to download and maintain a separate Eclipse installation for the API baseline. You can simply use a target definition file, as explained below.

To set up the API baseline, follow these steps:

  1. Select "Window -> Preferences". In the window that opens, select "Plug-in Development -> API Baselines" on the left pane.
  2. Click on "Add Baseline..."
  3. Choose "A target platform" and click Next.
  4. In the next page check the box "cdt-baseline".
  5. Click "Refresh" to download the contents of the target.
  6. Specify a name for this baseline in the top area, like "cdt-baseline" for example.
  7. Click "Finish", then "OK" in the next dialog.

Once this is done, a full build will be triggered. After that, any changes that doesn't follow API rules will be shown as an error.

Note that when a new version of CDT is released, you will need to refresh the baseline

  1. Go back to "Window -> Preferences", "Plug-in Development -> API Baselines"
  2. Select the cdt baseline and click on Edit...
  3. In the next page check the box "cdt-baseline".
  4. Click "Refresh" to update the contents of the target.
  5. Click "Finish", then "OK" in the next dialog.

(In the future, refreshing manually might not be required, see bug 479055)


All public API classes and interfaces must have meaningful javadoc header, as well as all public API members.

Contributing to CDT

See CDT/contributing

Applying the Patch

  • Assign bug to yourself
  • Set target milestone field to release in which patch would be applied, If it is applied in two branches set target milestone to maintenance branch
  • Code inspect the patch, apply and test
  • Commit the patch
  • Set the iplog as follows:
    • to '-' if the patch came from a committer
    • to '+' if the patch came from a non-committer.
  • If the patch is > 1,000 lines, it must be submitted for IP review, i.e. CQ in IPZilla. See Development_Resources/Automatic_IP_Log
  • Check that all non-committed patches are marked as obsolete
  • Change bug state to fixed. Check again that you set milestone field.
  • Add a comment about where it was fixed (branches) and related notes

Committing Code

  • API changes have to be discussed in cdt-dev mailing list before commiting
  • When development reaches cycle where release candidates are built, letter in cdt-dev should be sent for every commit you are making
  • Have a bug associated with every commit, with bug number at the beginning of commit comment, e.g.:
 Bug 12345 fixed that, added this
  • Post a change for review on gerrit
  • You may not need gerrit review if changes are cosmetic - formatting, warning fixed, copyright, auto-re factoring, typos in strings.

How to add a new feature

  • Create a feature project
  • Copy, epl-v10.html,, feature.xml, license.html from another cdt feature plugin
  • Open in feature editor and modify all feature specific details including plugin list
  • Add it to org.eclipse.cdt.repo/category.xml (see how other are done)
  • Add it to pom.xml file of the parent folder containing the feature. For example, qt/pom.xml needs to be modified if qt/org.eclipse.cdt.qt-feature was being added.

How to add a new plugin

  • Create a new plugin plugin
  • Version should be like 1.0.0.qualifier
  • Edit name and vendor. Externalize string. Bundle-Vendor = Eclipse CDT
  • Add your plugin to a feature
  • Open project properties Java Compiler -> Error and Warnings. Check "Enable project specific settings". Go through list of warnings and set some to errors (see above list of recommended settings). Some people prefer zero warning tolerance, in this case all of them should be errors and no warnings.
  • Make sure all packages are exported (or x-exported). See
  • Add it to pom.xml file of the parent folder containing the plugin. For example, qt/pom.xml needs to be modified if qt/org.eclipse.cdt.qt.core was being added.

Version Numbering

See Eclipse Version Numbering Guildlines

Bugs Workflow

For creating and managing bugs see

Back to the top