How to make Visual C++ recognize file extensions as C/C++ files

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Microsoft's Visual C++ Integrated Development Environment (IDE) recognizes the following file extensions as C++ source files: .c, .cpp, and .cxx. In some cases, a programmer may want to use other file extensions for C++ files; for example, Unix C++ source files often use the .cc extension.

Using the steps in this article, source files with other file extensions may benefit from the Visual C++ IDE's syntax coloring, automatic indentation, and other usage enhancements. This article describes how to automatically compile such files as C/C++ and associate the C++ icon with these files in Windows Explorer.


Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
322756 How to back up and restore the registry in Windows

The following procedure causes the Visual C++ IDE to recognize extensions other than .c, .cpp, and .cxx as a C/C++ source file. These changes involve altering registry settings.

To start the Registry Editor:
  1. Close any running instances of Developer Studio.
  2. On the Start menu, click Run.
  3. Type regedit and click OK to start the Registry Editor.
In the Registry Editor, repeat the following four steps for each new file extension to associate with a C/C++ icon. These steps illustrate how to associate the .cc file extension with the C++ source file icon:
  1. Right-click HKEY_CLASSES_ROOT and select New | Key.
  2. A key name will appear; change New Key #1 to .cc (the period is mandatory).
  3. Click the new .cc key, then double-click Default in the right-hand pane of the Registry Editor.
  4. In the Value Data field, type cppfile. Click OK.
Note To associate a file extension with the C source file icon, use cfile instead of cppfile. The values hppfile and hfile associate file extensions with C++ and C header file icons, respectively. (In Windows Explorer, the appropriate icon should now accompany files with the extension added in steps 1 through 4. Clicking the icon will launch Visual C++. Don't do this just yet, though.)

The following steps apply to keys and values located on the home key. In the Registry Editor, locate the user settings home key for Developer Studio. For various versions, the home key is:

Version 6.0 (ships with Visual Studio 6.0)


Version 5.0 (ships with Visual Studio 97)


Versions 4.x


The following registry keys cause the IDE to load the C/C++ compiler tool for the specified file extensions (.cc illustrated):

  1. Locate the following keys under Build System\Components\Platforms:
    Win32(ALPHA)\Tools\C/C++ Compiler for Alpha<BR/> Win32(PowerPC)\Tools\C/C++ Compiler for PowerPC<BR/> Win32(x86)\Tools\C/C++ Compiler for 80x86

    If WinCE 2.0 is installed, the following keys will also be present:
    Win32(WCE x86em)\Tools\C++ Compiler for 80x86em (Emulation)<BR/> Win32(WCE MIPS)\Tools\C/C++ Compiler Mips R4100<BR/> Win32(WCE SH)\Tools\C/C++ Compiler for SH<BR/>
  2. Each of those keys has a setting called Input_Spec. Double-click Input_Spec; then, in the Value Data field, add ;*.cc to the end of the existing list of extensions. Click OK.
The following registry key determines the file extensions selected for syntax coloring, smart indentation, and so on:

  1. Locate the key Text:
    Text Editor\Tabs/Language Settings\C/C++
  2. Double-click the FileExtensions setting; add ;cc to the end of the existing list of extensions. Click OK.
  3. Close the Registry Editor.
  4. Start Developer Studio and create a new file or open an existing one with the extension(s) just added. Syntax coloring and automatic indentation should be in effect.
Note The new extensions will not appear in the Files of type list when you click Open on the File menu. Use All Files (*.*) to view files with nonstandard extensions. Alternatively, double-click the file from Windows Explorer; once it loads into Visual C++, right-click inside the file's window and select Insert File into Project to add the file to a project.

Note External makefiles that are generated from Developer Studio will not have the correct inference rules for new file extensions. Inference rules must be added by either copying existing rules within the makefile (for example, adding at the beginning of the makefile and copying the .cpp.obj: rule to create a .cc.obj: rule), or by adding rules in the TOOLS.INI file.

Although the IDE starts the C/C++ compiler tool for the file extensions added in the steps above, the compiler needs to know whether to compile the file as C or C++. The compiler normally compiles .c files as C, and compiles .cpp and .cxx as C++. For all other extensions, the compiler needs an explicit parameter: /TC compiles files as C, /TP compiles files as C++. Each project that includes files with custom extensions needs an explicit /TC or /TP parameter. The following steps illustrate how to do this:
  1. Open a project in Developer Studio.
  2. Click Settings on the Project menu.
  3. In the resulting dialog box, select a configuration and a project (do not select All Configurations or multiple projects).
  4. Click the C/C++ tab.
  5. In the Project Options text box at the bottom, add /TP or /TC to the end of the listed options.
  6. Repeat steps 3 through 5 for each configuration and each project in the workspace whose explicit compile type needs to be set. Click OK.
Note Using /Tp"" and /Tc"" nevertheless generates the warnings D4024 and D4027 with VC++ 6.0. However, with the registry changes mentioned here, the file is properly compiled as the type specified. You may disregard the warnings in this case.

This setting treats ALL source files built by the CL compiler tool in the project as C++ (/TP) or C (/TC) files (the project options cannot be edited on a per-file basis). The entire project now uses either the C++ compiler or the C compiler. To treat individual files in a project as C++ or C source files, use the /Tp<source file> or /Tc<source file> settings. See REFERENCES for more information on the use of compiler settings.

If necessary, a custom build step can launch the C/C++ compiler (CL.EXE) with settings specific to a single file. This is less desirable, because the custom build step requires explicitly listing all of the compiler options. See REFERENCES for online documentation of instructions on adding a custom build step.


Visual C++ Programmer's Guide, Compiling and Linking, Details, Compiler Reference.

Visual C++, Developer Studio Environment User's Guide, Working With Projects, How Do I... Topics: Working With Projects, Customizing a Build Process.


Article ID: 181506 - Last Review: November 2, 2005 - Revision: 4.2
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