Eclipse - Workspace preferences

From EdWiki

Workspace preferences

Eclipse has some unusual defaults, and this is one of the reasons sometimes Eclipse fails to meet beginner expectations. Fortunately this can be easily fixed, each time after creating a new workspace it is recommended to check and maybe change the settings below.

Locate the Preferences menu

Eclipse has lots of settings, and they are a bit confusing for beginners. Apart form various objects Properties, accessible with Right click in most situations, there are settings that apply to the entire workspace, and these settings are named Preferences, accessible in the top menu.

Save automatically and Text file encoding

Sometimes users are very confused to see that after the edit/compile/run cycle nothing changed in the program behavior, although the editor clearly shows the changes. Usually the main reason is that the file was not actually saved and the build process used the previous version of the file. To automatically save edited files before build,

  • go to the Eclipse menu Windows Preferences General Workspace Build
  • enable Save automatically before build


In the same page, select the default text file encoding to to UTF-8. Without this setting, special characters like diacritics, are generally replaced with question marks (for example the source files is shown as ??OS++ or even ��OS++).

  • in the Text file encoding section
  • click the Other button
  • select UTF-8 in the combo box

It is also recommended to:

  • check the New text file line delimiter to be set to Unix
  • disable the Build automatically option

When you’re done:


click the Apply button

Show line numbers

Although not critical, while editing source files, it is useful to see the line numbers, and also a hint that the line may be too long:

  • go to the Eclipse menu Window Preferences General Editors Text Editors
  • enable Show line numbers
  • enable Show print margin
  • set the Print margin column at 80
  • click the Apply button


Use active build configuration for indexing

Eclipse CDT has a very powerful indexer, which parses the source code on the fly and provides hints, auto-completion help, error reporting, etc while editing, without having to start the build process. For this indexer to be accurate, it must be in sync with the compiler, in terms of options and environment. For the indexer to automatically sync when changing from one configuration to another, check if the indexer was set to use the active configuration:

go to the Eclipse menu Window Preferences C/C++ Indexer enable Use active build configuration

click the Apply button


Editor folding

To better view the entire content of the source files, it is recommended to disable editor folding:

go to the Eclipse menu Window Preferences C/C++ Editor Folding disable Header Comments (in fact it is recommended to disable all foldings) click the Apply button


Code formatter

Eclipse CDT has a very useful feature allowing to automatically reformat a piece of code to comply to a given style. The recommended style is GNU. To set it:

  • go to the Eclipse menu Window Preferences C/C++ Code Style Formatter
  • in the Active profile: field, select GNU [built-in]


Except very special company policies, it is generally recommended to NOT change the individual formatter style, and to apply the GNU format to all source files in a project before committing to the repository.

However, there is one detail that need to be changed, and this is the tab processing policy.

For this, click the Edit… button.


Change the tab policy to Spaces only, and the indentation and tab size to 2.

Since these changes were applied to a built in style, it is not possible to save the settings directly, but it is very easy to create a new profile name (for example GNU with spaces), and possibly export it for archiving.

When done, click the OK button twice.

To reformat a file:

select the file in the go to the Eclipse menu Source Format

The same action can be triggered with a right click and a Source Format.

To check if the text indeed has spaces and not tabs, enable the Show Whitespace Characters:


Note: the solution to configure the editor to enter spaces instead of Tabs prevents editing special files that mandates Tabs, like Make files.

Build console

The build console is the place where the progress of the build process is presented, and where the compile/link errors are shown.

The CDT defaults need some tweaks, to increase the number of lines and to make the lines wrap:

go to the Eclipse menu Window Preferences C/C++ Build Console

  • enable Wrap lines on the console
  • enable Bring console to top when building
  • increase the Limit console output: field, for example from 500 to 5000 lines
  • click the Apply button


When all settings are done, click the Apply and Close button.

Debug previous application

Another Eclipse default that needs to be changed is the way programs are debugged. Eclipse remembers the previous debug configuration used and can present it as the default for the main debug button.

To change this setting:

  • go to the Eclipse menu Window Preferences Run/Debug Launching
  • select Always launch the previously launched application in the Launch Operation section.


Show source roots

For large projects, with many source folders, you might want to disable showing the source folders:

go to the Eclipse menu Window Preferences C/C++ Appearance disable Show source roots at top of project.