CMake¶

Since Rice is header library, it is easy to use alternative build systems instead of Ruby and mkmf-rice. Rice itself uses CMake for building its test suite.

Getting started with CMake is easy. An example CMakeLists.txt file is shown below:

cmake_minimum_required (VERSION 3.26)

project(MyExtensionLibrary)

set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

# For older versions of CMake can use include("./FindRuby.cmake")
find_package("Ruby")

if (CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
    set(CMAKE_MSVC_DEBUG_INFORMATION_FORMAT "$<IF:$<AND:$<C_COMPILER_ID:MSVC>,$<CXX_COMPILER_ID:MSVC>>,$<$<CONFIG:Debug,RelWithDebInfo>:EditAndContinue>,$<$<CONFIG:Debug,RelWithDebInfo>:ProgramDatabase>>")
    add_compile_definitions(-D_CRT_SECURE_NO_DEPRECATE -D_CRT_NONSTDC_NO_DEPRECATE)
    add_compile_options(/bigobj /utf-8)
    # The default of /EHsc crashes Ruby when calling longjmp with optimizations on (/O2)
    string(REGEX REPLACE "/EHsc" "/EHs" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
elseif (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
    add_compile_definitions(-D_CRT_SECURE_NO_WARNINGS)
elseif (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
    add_compile_options(-ftemplate-backtrace-limit=0)
    # https://github.com/doxygen/doxygen/issues/9269#issuecomment-1094975328
    add_compile_options(unittest PRIVATE -Wa,-mbig-obj)
endif ()

add_library (MyExtension SHARED
             "MyExtension.cpp")

target_include_directories(sample_callbacks PRIVATE ${Ruby_INCLUDE_DIR} ${Ruby_CONFIG_INCLUDE_DIR})
target_include_directories(sample_callbacks PRIVATE ${PROJECT_SOURCE_DIR})
target_link_libraries(sample_callbacks ${Ruby_LIBRARY})

target_include_directories(sample_callbacks PRIVATE rice)

Note that Rice requires C++17. Then it search for Ruby, sets various compiler settings and finally defines a new library called MyExtension which is a Ruby extension.

FindRuby¶

After creating a CMake project, you will want to locate Ruby. This is done like this:

# For older versions of CMake can use include("./FindRuby.cmake")
find_package("Ruby")

This sets the following CMake CACHE variables:

Variable	Description
Ruby_VERSION_MAJOR	Ruby major version
Ruby_VERSION_MINOR	Ruby minor version
Ruby_VERSION_PATCH	Ruby patch version
Ruby_ARCH_DIR	Ruby arch dir
Ruby_HDR_DIR	Ruby header dir (1.9+)
Ruby_ARCHHDR_DIR	Ruby arch header dir (2.0+)
Ruby_RUBY_LIB_DIR	Ruby ruby-lib dir
Ruby_SITEARCH_DIR	Ruby site arch dir
Ruby_SITELIB_DIR	Ruby site lib dir
Ruby_EXECUTABLE	Ruby interpreter
Ruby_LIBRARY	Ruby shared library
Ruby_INCLUDE_DIR	Ruby include directory
Ruby_CONFIG_INCLUDE_DIR	Ruby config include directory
Ruby_INCLUDE_DIRS	Include and config directories

Compiler Settings¶

On Windows, for both GCC (MinGW) and MSVC you have to turn on big object support. For MSVC, you will want to turn on UTF-8 since there are UTF-8 characters in the comments of the source code. See Automatically Generated Ruby Classes.