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How to Create A Shared Library With Cmake?

6 minutes read

To create a shared library with CMake, you first need to define your library in a CMakeLists.txt file. This file should include the project name, any source files that will be compiled to create the library, and any dependencies that the library may have.


Next, you will need to use the add_library() function in CMake to create your shared library. This function takes the name of the library as the first argument, followed by the type of library you want to create (SHARED for shared libraries), and the source files that will be compiled to create the library.


Once you have defined your shared library in the CMakeLists.txt file, you can now build your project using CMake. When you run the CMake command in your terminal, it will generate the necessary build files for your shared library based on the instructions in your CMakeLists.txt file.


After running CMake, you can then use a build tool like make or Visual Studio to compile your shared library. Once your shared library has been successfully built, you can then link it to other projects or applications that require its functionality. This can be done by specifying the location of the shared library in the CMakeLists.txt file of the project that will be using it.


How to set the soname for a shared library in cmake?

You can set the soname for a shared library in CMake by using the SET_TARGET_PROPERTIES command. Here is an example of how you can set the soname for a shared library named mylib:

  1. Create a CMakeLists.txt file in the root directory of your project
  2. Add the following code to the CMakeLists.txt file: 
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cmake_minimum_required(VERSION 3.0)

project(MyProject)

add_library(mylib SHARED mylib.cpp)

# Set the soname for the shared library
set_target_properties(mylib PROPERTIES
    SOVERSION 1
)


In this example, the SOVERSION property is set to 1, which will set the soname of the shared library to mylib.so.1.

  1. Run cmake . to generate the build files
  2. Build your project using make or your preferred build tool
  3. Once the shared library is built, you can verify the soname by running the readelf -a command and looking for the SONAME field in the output.


What is the best practice for organizing source files in a shared library project?

There are several best practices for organizing source files in a shared library project:

  1. Use a logical folder structure: Group related files together in folders based on their functionality or module. For example, separate folders for interfaces, classes, enums, etc.
  2. Use meaningful file names: Give your source files descriptive names that reflect their purpose and content. This will make it easier for developers to understand the codebase.
  3. Follow a consistent naming convention: Establish a consistent naming convention for your files and stick to it throughout the project. This will make it easier to locate files and understand their purpose.
  4. Use package organization: If using a language that supports packages or namespaces, organize your source files into packages or namespaces to prevent naming conflicts and improve code readability.
  5. Keep dependencies organized: If your shared library project depends on external libraries or frameworks, keep them organized in a separate folder and document the dependencies properly.
  6. Utilize version control: Use a version control system like Git to track changes to your codebase and manage collaboration with team members. This will ensure that everyone is working on the latest version of the code and allow for easy rollback if needed.
  7. Document your code: Add comments and documentation to your source files to explain the purpose of classes, methods, and variables. This will make it easier for other developers to understand how the code works and how to use your library.


By following these best practices, you can ensure that your shared library project is well-organized, easy to maintain, and accessible to team members.


How to create a shared library with cmake?

To create a shared library with CMake, follow these steps:

  1. Create a CMakeLists.txt file in your project directory and add the following code:
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cmake_minimum_required(VERSION 3.10)
project(MyLibrary)

set(CMAKE_CXX_STANDARD 11)

# Define the sources for your library
set(SOURCES
    source1.cpp
    source2.cpp
    source3.cpp
)

# Create the shared library
add_library(MyLibrary SHARED ${SOURCES})

# Set the output directory for the shared library
set_target_properties(MyLibrary PROPERTIES
    LIBRARY_OUTPUT_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/lib
)


  1. Create your source files (e.g., source1.cpp, source2.cpp, source3.cpp) in the same directory as the CMakeLists.txt file.
  2. Open a terminal and navigate to your project directory. Create a build directory and navigate to it: 
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mkdir build
cd build


  1. Run CMake to generate the build files:
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cmake ..


  1. Build the shared library by running make:
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make


  1. Your shared library should now be built and located in the "lib" directory in your project folder.


You can link against this shared library in other CMake projects by adding the following lines to their CMakeLists.txt file:

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find_library(MyLibrary_lib MyLibrary PATHS ${CMAKE_CURRENT_SOURCE_DIR}/lib)
target_link_libraries(MyExecutable ${MyLibrary_lib})



How to create a shared library with specific versioning requirements in cmake?

To create a shared library with specific versioning requirements in CMake, you can use the "SOVERSION" property of the "add_library" command. Here's an example of how you can do this:

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cmake_minimum_required(VERSION 3.5)
project(MyLibrary)

# Add the shared library with version information
add_library(MyLibrary SHARED 
    src/mylibrary.cpp
)

# Set the version of the shared library
set_target_properties(MyLibrary PROPERTIES 
    SOVERSION 1
    VERSION 1.0
)

# Specify installation destination for the library
install(TARGETS MyLibrary 
    LIBRARY DESTINATION lib
)


In this example, the "SOVERSION" property is set to 1, which means that the library will have a soname of "MyLibrary.so.1" when installed on the system. The "VERSION" property is set to 1.0, which indicates the version of the library itself.


When you build your project using this CMake configuration, the shared library will be created with the specified versioning requirements. You can then install the library using the "install" command, which will place the library in the specified destination with the correct version information.


How to specify compiler flags for building a shared library with cmake?

To specify compiler flags for building a shared library with CMake, you can use the add_library and target_compile_options commands in your CMakeLists.txt file. Here's how you can do it:

  1. Use the add_library command to create your shared library target. For example:
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add_library(my_shared_library SHARED source1.cpp source2.cpp)


  1. Use the target_compile_options command to specify the compiler flags for your shared library target. For example, to add the -Wall flag:
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target_compile_options(my_shared_library PRIVATE -Wall)


You can add multiple compiler flags by separating them with spaces. For example:

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target_compile_options(my_shared_library PRIVATE -Wall -O2)


  1. After specifying the compiler flags, you can continue with the rest of your CMake configuration for building the shared library.


By following these steps, you can specify compiler flags for building a shared library with CMake.


How to link a shared library with cmake?

To link a shared library with CMake, you need to follow these steps:

  1. Use the find_library function in your CMakeLists.txt file to locate the shared library on your system. For example, if you want to link the mylib library, you can add the following line to your CMakeLists.txt file:
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find_library(MYLIB_LIB mylib)


  1. Add the shared library to the target by using the target_link_libraries function. For example, if you have a target called myapp, you can link the mylib library to it by adding the following line to your CMakeLists.txt file:
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target_link_libraries(myapp ${MYLIB_LIB})


  1. Make sure to include the appropriate include directories for the shared library if needed by using the target_include_directories function. For example, if the mylib library requires including headers from a directory called mylib/include, you can add the following line to your CMakeLists.txt file:
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target_include_directories(myapp PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/mylib/include)


  1. Finally, run CMake to generate the appropriate build scripts and build your project to link the shared library with your executable.
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