To create a precompiled header file, you must first open a project. The settings from this project are used when precompiling. A file to be precompiled does not have to be a header file (".h" or ".hpp"), but it must meet these requirements:

• The file must be a text file. You cannot precompile libraries or other files.
• The file must be saved with a recognized extension, such as ".pch" or ".pch++," at the end of its file name.
• The file does not have to be in a project, although a project must be open to precompile.
• The file must not contain any statements that generate data or code. However, C++ source code can contain inline functions and constant variable declarations (const).
• Precompiled header files for different build targets are not interchangeable. For example, to generate a precompiled header for use with Win32 compilers, you must use a Win32 compiler.
• A source file can include only one precompiled header file using the #include directive.

After you save the text file, the IDE can use that text file to create a precompiled header. You can specify the name of the precompiled header at the time of precompilation. You can also specify the name by including the following line at the beginning of your text file, where name is the name you wish to call the precompiled header:

Append the extension ".mch" to name. This extension is required for precompiled headers.

To precompile a saved text file, choose Precompile from the Project Menu. This command precompiles the text file in the active window, creating a precompiled header file. If compiler errors are detected, a Message window appears.

To learn more about the Message window and correcting compiler errors, consult "Correcting Compiler Errors and Warnings."

To learn more about automatic updating of precompiled headers, see the next section, "Automatic updating."

If the source code has been modified, the CodeWarrior IDE automatically updates a precompiled header during a Make or Bring Up To Date operation.

If CodeWarrior encounters a ".pch" or ".pch++" file that was modified since it was last precompiled, the IDE precompiles it again to ensure that the resulting precompiled header is up-to-date.

To create a precompiled header file that is automatically updated, open the project that uses the precompiled header. Then, create a text file that will be used to create the precompiled header.

To read about the requirements for a precompiled header text file, refer to "Creating Precompiled Headers".

In the first line of the text file, add the line:

This pragma tells the compiler to create a precompiled header with the file name of name.

Append the extension ".mch" to name. This extension is required for precompiled headers.

When you finish the text file, save it with a valid extension in the same folder as your project.

Save the text file with a ".pch" extension if it will be used to create a precompiled header in either C or C++.

Save the text file with a ".pch" extension if it will be used to create a precompiled header in C. Use the ".pch++" extension if the text file will be used to create a precompiled header in C++.

Next, choose Precompile from the Project Menu.

Now add the text file to the open project using the Add Window command in the Project Menu.

Whenever the precompiled header file is modified, the CodeWarrior project manager automatically updates the header file by precompiling it.

To include the precompiled header in a project source-code file, add this line as the first #include directive in the source-code file:

Alternatively, you can specify a precompiled header as a prefix file, using the settings for your build target. To learn how to do this, refer to the discussion of the C/C++ Language settings panel in the C Compiler Guide.