For each platform and operating system, there are two build environments: one for building free binaries and one for building checked binaries.

In the free build environment, the Build utility generates a build product that is optimized for release, similar to a retail build created with Microsoft Visual Studio.

In the checked build environment, the Build utility generates a build product that has a number of features that facilitate testing and debugging:

• In the checked environment, the Build utility does not optimize the code it creates.
• Checked binaries (products built in the checked environment) typically have extra tests in the code to catch errors.
• The checked environment also defines the DBG preprocessor constant, which controls whether certain debugging routines are called. For more information, see Conditional Compilation and the Build Environment.

All drivers should first be compiled and tested in the checked environment. Builds must be recompiled and retested in the free environment after they are complete and have been demonstrated to work.

Note  The free and checked build environments are not related to the free and checked builds of the Windows operating system. For information about the free and checked builds of the Windows operating system, see Using the Checked Build.