Example Code: Using CMAKE_MFC_FLAG for Static and Shared MFC Linking

What is CMAKE_MFC_FLAG?

In CMake, CMAKE_MFC_FLAG is a variable used to control how your project links with the Microsoft Foundation Classes (MFC) library. It determines whether to use the static or shared version of MFC when generating project files, primarily for Visual Studio.

Possible Values

• 2
  Links with the shared MFC library (DLLs). This creates a smaller executable or DLL but requires the presence of the corresponding MFC DLLs on the target system at runtime.
• 1
  Links with the static MFC library. This creates a self-contained executable or DLL that doesn't rely on external MFC DLLs at runtime.

How to Use CMAKE_MFC_FLAG

1. • You can set CMAKE_MFC_FLAG directly in your CMakeLists.txt file using the set command:

   set(CMAKE_MFC_FLAG 1)  # Link with static MFC library
   # or
   set(CMAKE_MFC_FLAG 2)  # Link with shared MFC library
   

2. Conditional Linking (Optional)
   

   • If you want to choose the MFC linking option based on certain conditions, you can use conditional statements:

   if(NOT WINDOWS_STORE_APP)  # Avoid static linking for Windows Store apps
     set(CMAKE_MFC_FLAG 1)
   endif()
   

Important Considerations

• Choose the linking method (static or shared) based on your project's requirements and deployment considerations. Static linking creates larger executables but avoids runtime dependencies on MFC DLLs. Shared linking results in smaller executables but requires the MFC DLLs to be present at runtime.
• For other build systems or IDEs, you might need to set compiler and linker flags specific to that environment.
• CMAKE_MFC_FLAG primarily affects the generation of Visual Studio project files. It doesn't directly control the compiler or linker flags used during the build process.

---

Example 1: Linking with Static MFC Library

# Link with static MFC library by default
set(CMAKE_MFC_FLAG 1)

# Project configuration
project(MyMFCProject)
cmake_minimum_required(VERSION 3.0)

# Find required libraries (adjust as needed)
find_package(MFC REQUIRED)

# Add your source files here
add_executable(my_app main.cpp other_source.cpp)

# Target specific linking (optional)
if(WIN32)
  target_link_libraries(my_app PRIVATE ${MFC_LIBRARIES})
else()
  # Handle non-Windows platforms (if applicable)
endif()

1. set(CMAKE_MFC_FLAG 1) sets the default linking method to static MFC.
2. The find_package(MFC REQUIRED) line ensures that CMake finds the MFC libraries during configuration.
3. The add_executable command creates an executable named my_app from the source files.
4. The optional target_link_libraries command (within the if(WIN32) block) explicitly links the target my_app with the MFC libraries found by find_package(MFC). This step might not be strictly necessary as CMake should handle linking based on CMAKE_MFC_FLAG.

# Choose linking method based on platform
if(WIN32)
  set(CMAKE_MFC_FLAG 1)  # Static linking on Windows
else()
  set(CMAKE_MFC_FLAG 2)  # Shared linking on other platforms
endif()

# Project configuration (rest of your CMakeLists.txt)

1. This code snippet sets CMAKE_MFC_FLAG to 1 (static) for Windows and 2 (shared) for other platforms using an if statement.
2. The rest of your project configuration (source files, targets, etc.) would follow as usual.

---

Compiler and Linker Flags

• The specific flags depend on your compiler and environment. For example, with Visual Studio command line tools (cl.exe), you might use:

  • /MT for static linking
  • /MD for shared linking

• If you're not using Visual Studio or a CMake-generated project file, you might need to set compiler and linker flags directly to specify the MFC library usage.

IDE-Specific Settings

• Many IDEs (like Code::Blocks, Eclipse with CDT) have built-in options to configure linking with MFC. These options might be located in project properties or compiler/linker settings.

Build System Integration

• If you're using a custom build system or one different from CMake, you might need to integrate MFC library linking logic into your build scripts. This would involve explicitly specifying the MFC libraries and linking flags appropriate for your system.

Approach	Description
Compiler/Linker Flags	Set flags directly during compilation (e.g., /MT, /MD)
IDE-Specific Settings	Use IDE options to configure MFC linking (project properties)
Build System Integration	Integrate MFC linking logic into your custom build scripts

Choosing the Right Approach

The best approach depends on your development environment and build system:

• For other build systems or IDEs, explore their built-in MFC linking options or adapt your build scripts accordingly.
• If you're using Visual Studio and CMake, CMAKE_MFC_FLAG is a convenient way to handle MFC linking.

• If you encounter issues, refer to the documentation for your specific compiler, linker, or build system for instructions on linking with MFC.
• Consider using a package manager like vcpkg (for C++ libraries) to manage dependencies like MFC, which can simplify linking setup.