CMakeAddFortranSubdirectory

This module provides a command to add a Fortran project located in a subdirectory.

Load this module in a CMake project with:

include(CMakeAddFortranSubdirectory)

Commands

This module provides the following command:

cmake_add_fortran_subdirectory

Adds a Fortran-only subproject from subdirectory to the current project:

cmake_add_fortran_subdirectory(
  <subdir>
  PROJECT <project-name>
  ARCHIVE_DIR <dir>
  RUNTIME_DIR <dir>
  LIBRARIES <libs>...
  LINK_LIBRARIES
    [LINK_LIBS <lib> <deps>...]...
  [CMAKE_COMMAND_LINE <flags>...]
  NO_EXTERNAL_INSTALL
)

This command checks whether the current compiler supports Fortran or attempts to locate a Fortran compiler. If a compatible Fortran compiler is found, the Fortran project located in <subdir> is added as a subdirectory to the current project.

If no Fortran compiler is found and the compiler is MSVC, it searches for the MinGW gfortran compiler. In this case, the Fortran project is built as an external project using MinGW tools, and Fortran-related imported targets are created. This setup works only if the Fortran code is built as a shared DLL library, so the BUILD_SHARED_LIBS variable is enabled in the external project. Additionally, the CMAKE_GNUtoMS variable is set to ON to ensure that Microsoft-compatible .lib files are created.

The options are:

PROJECT

The name of the Fortran project as defined in the top-level CMakeLists.txt located in <subdir>.

ARCHIVE_DIR

Directory where the project places .lib archive files. A relative path is interpreted as relative to CMAKE_CURRENT_BINARY_DIR.

RUNTIME_DIR

Directory where the project places .dll runtime files. A relative path is interpreted as relative to CMAKE_CURRENT_BINARY_DIR.

LIBRARIES

Names of library targets to create or import into the current project.

LINK_LIBRARIES

Specifies link interface libraries for LIBRARIES. This option expects a list of LINK_LIBS <lib> <deps>... items, where:

• LINK_LIBS marks the start of a new pair
• <lib> is a library target.
• <deps>... represents one or more dependencies required by <lib>.

CMAKE_COMMAND_LINE

Additional command-line flags passed to cmake(1) command when configuring the Fortran subproject.

NO_EXTERNAL_INSTALL

Prevents installation of the external project.

Note

The NO_EXTERNAL_INSTALL option is required for forward compatibility with a future version that supports installation of the external project binaries during make install.

Examples

Adding a Fortran subdirectory to a project can be done by including this module and calling the cmake_add_fortran_subdirectory() command. In the following example, a Fortran project provides the hello library and its dependent world library:

include(CMakeAddFortranSubdirectory)

cmake_add_fortran_subdirectory(
  fortran-subdir
  PROJECT FortranHelloWorld
  ARCHIVE_DIR lib
  RUNTIME_DIR bin
  LIBRARIES hello world
  LINK_LIBRARIES
    LINK_LIBS hello world # hello library depends on the world library
  NO_EXTERNAL_INSTALL
)

# The Fortran target can be then linked to the main project target.
add_executable(main main.c)
target_link_libraries(main PRIVATE hello)

See Also

There are multiple ways to integrate Fortran libraries. Alternative approaches include:

• The add_subdirectory() command to add the subdirectory directly to the build.
• The export() command can be used in the subproject to provide Imported Targets or similar for integration with other projects.
• The FetchContent or ExternalProject modules when working with external dependencies.