CMake の共有ライブラリのリンカフラグを初期化する変数 CMAKE_SHARED_LINKER_FLAGS_CONFIG_INIT

CMake 変数 CMAKE_SHARED_LINKER_FLAGS_CONFIG_INIT の詳細解説

CMAKE_SHARED_LINKER_FLAGS_CONFIG_INIT は、CMake のビルドプロセスにおいて、共有ライブラリのリンカフラグを初期化する変数です。この変数は、toolchain file 内で設定され、CMake がビルドツリーを初めて構成する際に使用されます。CMake は、環境やターゲットプラットフォームに基づいて、この変数の値に内容を前置または付加することがあります。

詳細

• 目的: 共有ライブラリのリンカフラグを初期化します。
• 設定場所: toolchain file
• 使用タイミング: CMake がビルドツリーを初めて構成する際
• 処理: CMake は、環境やターゲットプラットフォームに基づいて、この変数の値に内容を前置または付加することがあります。

利点

• 異なるプラットフォームやコンパイラ間で共有ライブラリのリンカフラグを統一的に設定できます。
• ビルドプロセスを簡素化し、コードの移植性を向上させることができます。

例

# toolchain file 例

set(CMAKE_SHARED_LINKER_FLAGS_CONFIG_INIT "-Wl,-rpath,${CMAKE_INSTALL_PREFIX}/lib")

この例では、共有ライブラリのリンカフラグに -Wl,-rpath,${CMAKE_INSTALL_PREFIX}/lib が設定されます。これは、CMake がインストールした共有ライブラリを検索するパスをリンカに指示します。

補足

• CMAKE_SHARED_LINKER_FLAGS_CONFIG_INIT は、CMake 3.7 以降で使用できます。

関連変数

• CMAKE_SHARED_LINKER_FLAGS: 共有ライブラリのリンカフラグを設定します。
• CMAKE_TOOLCHAIN_FILE: toolchain file の場所を設定します。

CMAKE_SHARED_LINKER_FLAGS_CONFIG_INIT は、CMake における共有ライブラリのリンカフラグ設定を簡素化し、移植性を向上させるための有用な変数です。

• 本解説は、プログラミングの専門知識を持たない方でも理解しやすいように、分かりやすく記述しています。
• 具体的な設定方法や詳細な技術情報については、上記の情報源を参照してください。

Example 1: Setting a library search path

# toolchain file example

set(CMAKE_SHARED_LINKER_FLAGS_CONFIG_INIT "-Wl,-rpath,${CMAKE_INSTALL_PREFIX}/lib")

This example sets the library search path for shared libraries to the directory CMAKE_INSTALL_PREFIX/lib. This means that CMake will look for shared libraries in this directory when linking an executable.

Example 2: Adding a linker flag for a specific platform

# toolchain file example

if(CMAKE_SYSTEM_NAME MATCHES "Linux")
  set(CMAKE_SHARED_LINKER_FLAGS_CONFIG_INIT "-Wl,--no-as-needed")
endif()

This example adds the linker flag -Wl,--no-as-needed to the CMAKE_SHARED_LINKER_FLAGS_CONFIG_INIT variable if the system is Linux. This flag tells the linker to not automatically add dependent libraries to the link command.

Example 3: Using a variable to set a linker flag

# toolchain file example

set(LIBRARY_SEARCH_PATH "${CMAKE_INSTALL_PREFIX}/lib")

set(CMAKE_SHARED_LINKER_FLAGS_CONFIG_INIT "-Wl,-rpath,${LIBRARY_SEARCH_PATH}")

This example sets the LIBRARY_SEARCH_PATH variable to the directory CMAKE_INSTALL_PREFIX/lib and then uses this variable to set the library search path for shared libraries.

Example 4: Using a function to set a linker flag

# toolchain file example

function(add_linker_flag flag)
  set(CMAKE_SHARED_LINKER_FLAGS_CONFIG_INIT "${CMAKE_SHARED_LINKER_FLAGS_CONFIG_INIT} ${flag}")
endfunction()

add_linker_flag("-Wl,-rpath,${CMAKE_INSTALL_PREFIX}/lib")

This example defines a function add_linker_flag() that takes a linker flag as input and adds it to the CMAKE_SHARED_LINKER_FLAGS_CONFIG_INIT variable. The function is then called to add the library search path flag -Wl,-rpath,${CMAKE_INSTALL_PREFIX}/lib.

Example 5: Using a CMakeLists.txt file to set a linker flag

# CMakeLists.txt example

set(CMAKE_TOOLCHAIN_FILE path/to/toolchain.cmake)

project(myproject)

add_executable(myprogram myprogram.cpp)

target_link_libraries(myprogram mylibrary)

This example sets the CMAKE_TOOLCHAIN_FILE variable to the path of the toolchain file and then uses the target_link_libraries() command to link the mylibrary library to the myprogram executable. The linker flags defined in the toolchain file will be used when linking the executable.

These are just a few examples of how to use the CMAKE_SHARED_LINKER_FLAGS_CONFIG_INIT variable. There are many other ways to use this variable to configure linker flags for your CMake projects.

I hope this helps! Let me know if you have any other questions.

The CMAKE_SHARED_LINKER_FLAGS variable can be used to set linker flags for all shared libraries that are linked to a target. This variable can be set in either the CMakeLists.txt file or the toolchain file.

Example:

# CMakeLists.txt example

set(CMAKE_SHARED_LINKER_FLAGS "-Wl,-rpath,${CMAKE_INSTALL_PREFIX}/lib")

project(myproject)

add_executable(myprogram myprogram.cpp)

target_link_libraries(myprogram mylibrary)

This example sets the library search path for shared libraries to the directory CMAKE_INSTALL_PREFIX/lib. This means that CMake will look for shared libraries in this directory when linking any executable.

Using the target_link_options() command:

The target_link_options() command can be used to set linker flags for a specific target. This command can be used in the CMakeLists.txt file to set linker flags for executables, shared libraries, and static libraries.

Example:

# CMakeLists.txt example

project(myproject)

add_executable(myprogram myprogram.cpp)

target_link_options(myprogram "-Wl,-rpath,${CMAKE_INSTALL_PREFIX}/lib")

target_link_libraries(myprogram mylibrary)

This example sets the library search path for the myprogram executable to the directory CMAKE_INSTALL_PREFIX/lib. This means that CMake will look for shared libraries in this directory when linking the myprogram executable.

Using a CMakeLists.txt file to set linker flags per source file:

CMake allows you to set linker flags for specific source files using the target_sources() command. This can be useful if you need to use different linker flags for different parts of your code.

Example:

# CMakeLists.txt example

project(myproject)

add_executable(myprogram myprogram.cpp foo.cpp bar.cpp)

target_sources(myprogram PUBLIC myprogram.cpp)
target_sources(myprogram PRIVATE foo.cpp)
target_sources(myprogram PRIVATE bar.cpp)

target_link_options(myprogram PUBLIC "-Wl,-rpath,${CMAKE_INSTALL_PREFIX}/lib1")
target_link_options(myprogram PRIVATE "-Wl,-rpath,${CMAKE_INSTALL_PREFIX}/lib2")

target_link_libraries(myprogram mylibrary)

This example sets the library search path for the myprogram executable to the directory CMAKE_INSTALL_PREFIX/lib1 for the myprogram.cpp source file and to the directory CMAKE_INSTALL_PREFIX/lib2 for the foo.cpp and bar.cpp source files.

Using a custom CMake command:

You can also use a custom CMake command to set linker flags. This can be useful if you need to set linker flags that are not supported by the built-in CMake commands.

Example:

# CMakeLists.txt example

project(myproject)

add_executable(myprogram myprogram.cpp)

add_custom_command(TARGET myprogram
                  COMMAND ${CMAKE_LINKER} ${CMAKE_ARGS} $<TARGET_SOURCES> $<TARGET_LINK_LIBRARIES> -Wl,-rpath,${CMAKE_INSTALL_PREFIX}/lib)

This example sets the library search path for the myprogram executable to the directory CMAKE_INSTALL_PREFIX/lib using a custom CMake command.

These are just a few of the many ways to configure linker flags for your CMake projects. The best method for you will depend on your specific needs.

I hope this helps! Let me know if you have any other questions.