LIB_PREFIX: 設置生成庫的前綴 SET(LIB_PREFIX g2o_)

# The library prefix
SET(LIB_PREFIX g2o_)

變量的默認配置

# default built type
IF(NOT CMAKE_BUILD_TYPE)
  SET(CMAKE_BUILD_TYPE Release CACHE STRING
      "Choose the type of build, options are: None Debug Release RelWithDebInfo MinSizeRel."
      FORCE)
ENDIF(NOT CMAKE_BUILD_TYPE)
 

CMAKE_DEBUG_POSTFIX ,CMAKE_RELEASE_POSTFIX,CMAKE_RELWITHDEBINFO_POSTFIX,CMAKE_MINSIZEREL_POSTFIX：不同版本生成庫的不同後綴聲明變量

# postfix, based on type
SET(CMAKE_DEBUG_POSTFIX "_d" CACHE STRING "postfix applied to debug build of libraries")
SET(CMAKE_RELEASE_POSTFIX "" CACHE STRING "postfix applied to release build of libraries
 
")
SET(CMAKE_RELWITHDEBINFO_POSTFIX "_rd" CACHE STRING "postfix applied to release-with-debug-information libraries")
SET(CMAKE_MINSIZEREL_POSTFIX "_s" CACHE STRING "postfix applied to minimium-size-build libraries")

EXE_POSTFIX：生成ELF文件的後綴

IF(CMAKE_BUILD_TYPE MATCHES Release)
  SET(EXE_POSTFIX)
ELSEIF(CMAKE_BUILD_TYPE MATCHES Debug)
  SET(EXE_POSTFIX ${CMAKE_DEBUG_POSTFIX})
ELSEIF(CMAKE_BUILD_TYPE MATCHES RelWithDebInfo)
  SET(EXE_POSTFIX ${CMAKE_RELWITHDEBINFO_POSTFIX})
ELSEIF(CMAKE_BUILD_TYPE MATCHES MinSizeRel)
  SET(EXE_POSTFIX ${CMAKE_MINSIZEREL_POSTFIX})
ENDIF(CMAKE_BUILD_TYPE MATCHES Release)
 

允許客戶選擇的構建庫的類型

# Allow the developer to select if Dynamic or Static libraries are built
OPTION (BUILD_SHARED_LIBS "Build Shared Libraries (preferred and required for the g2o plugin system)" ON)
SET (G2O_LIB_TYPE STATIC)
IF (BUILD_SHARED_LIBS)
  SET (G2O_LIB_TYPE SHARED)
ENDIF()

bin和libs輸出路徑

# Set the output directory for the build executables and libraries
SET(g2o_RUNTIME_OUTPUT_DIRECTORY ${g2o_SOURCE_DIR}/bin CACHE PATH "Target for the binaries")
IF(WIN32)
  SET(g2o_LIBRARY_OUTPUT_DIRECTORY ${g2o_SOURCE_DIR}/bin CACHE PATH "Target for the libraries")
ELSE(WIN32)
  SET(g2o_LIBRARY_OUTPUT_DIRECTORY ${g2o_SOURCE_DIR}/lib CACHE PATH "Target for the libraries")
ENDIF(WIN32)
SET(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${g2o_LIBRARY_OUTPUT_DIRECTORY})
SET(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${g2o_LIBRARY_OUTPUT_DIRECTORY})
SET(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${g2o_RUNTIME_OUTPUT_DIRECTORY})

聲明其他模塊的位置

# Set search directory for looking for our custom CMake scripts to
# look for SuiteSparse, QGLViewer, and Eigen3.
LIST(APPEND CMAKE_MODULE_PATH ${g2o_SOURCE_DIR}/cmake_modules)

根據不同操作系統選擇不同宏定義

# Detect OS and define macros appropriately
IF(WIN32)
  ADD_DEFINITIONS(-DWINDOWS)
  MESSAGE(STATUS "Compiling on Windows")
  IF(MSVC)
    MESSAGE(STATUS "Compiling with MSVC")
    ADD_DEFINITIONS(-DNOMINMAX)
    ADD_DEFINITIONS(-D_USE_MATH_DEFINES)
    # SSE2 optimizations
    if(NOT CMAKE_SIZEOF_VOID_P EQUAL 8)  # No need to specify if building for x64 (actually, it generates an annoying warning)
        ADD_DEFINITIONS("/arch:SSE2")
    endif()
    IF (BUILD_SHARED_LIBS)
      # disable warning on missing DLL interfaces
      ADD_DEFINITIONS("/wd4251")
    ENDIF()
    # Fix issue: https://github.com/RainerKuemmerle/g2o/issues/66
    #            Link error LNK2005 due to duplicated symbols
    add_definitions("/Ob2")    
    # Fix other stupid warnings:
    add_definitions(-D_CRT_SECURE_NO_WARNINGS=1)  # Avoid deprecated fprintf(), etc.
    add_definitions("/nologo")
    add_definitions("/wd4244") # Conversion from double -> int
    add_definitions("/wd4267") # Conversion during return
    add_definitions("/wd4522") # Duplicated operator=() in Eigen headers
  ENDIF(MSVC)
ELSEIF(CYGWIN)
  MESSAGE(STATUS "Compiling on Cygwin")
  ADD_DEFINITIONS(-DCYGWIN)
ELSEIF(APPLE)
  ADD_DEFINITIONS(-DUNIX)
  MESSAGE(STATUS "Compiling on OSX")
ELSEIF(UNIX)
  ADD_DEFINITIONS(-DUNIX)
  MESSAGE(STATUS "Compiling on Unix")
ENDIF(WIN32)

# detect Android Cross Compiler
# based on android-cmake which sets the variable ANDROID for us
IF(ANDROID)
ADD_DEFINITIONS(-DANDROID)
MESSAGE(STATUS "Cross compiling for Android")
ENDIF()

查找模塊

# For building the CHOLMOD / CSPARSE solvers
FIND_PACKAGE(Cholmod)
FIND_PACKAGE(BLAS)
FIND_PACKAGE(LAPACK)
IF(CHOLMOD_FOUND AND BLAS_FOUND AND LAPACK_FOUND)
  MESSAGE(STATUS "Found CHOLMOD and its dependencies")
  SET(CHOLMOD_FOUND TRUE)
ELSE()
  SET(CHOLMOD_FOUND FALSE)
ENDIF()

FIND_PACKAGE(CSparse)
IF(CSPARSE_FOUND)
  SET(BUILD_CSPARSE OFF CACHE BOOL "Build local CSparse library")
ELSE(CSPARSE_FOUND)
  SET(BUILD_CSPARSE ON CACHE BOOL "Build local CSparse library")
  IF(BUILD_CSPARSE)
    SET(CSPARSE_FOUND TRUE)
  ENDIF()
ENDIF(CSPARSE_FOUND)
OPTION(BUILD_LGPL_SHARED_LIBS "Build LGPL Code as Shared Libraries (LGPL Code)" ON)
SET (G2O_LGPL_LIB_TYPE STATIC)
IF (BUILD_LGPL_SHARED_LIBS)
  SET (G2O_LGPL_LIB_TYPE SHARED)
ELSE()
  MESSAGE(STATUS "Building LGPL code as static library (affects license of the binary)")
ENDIF()

OpenNMP的加速表現不佳

# Eigen library parallelise itself, though, presumably due to performance issues
# OPENMP is experimental. We experienced some slowdown with it
SET(G2O_USE_OPENMP OFF CACHE BOOL "Build g2o with OpenMP support (EXPERIMENTAL)")
IF(G2O_USE_OPENMP)
  FIND_PACKAGE(OpenMP)
  IF(OPENMP_FOUND)
    SET (G2O_OPENMP 1)
    SET(g2o_C_FLAGS "${g2o_C_FLAGS} ${OpenMP_C_FLAGS}")
    SET(g2o_CXX_FLAGS "${g2o_CXX_FLAGS} -DEIGEN_DONT_PARALLELIZE ${OpenMP_CXX_FLAGS}")
    MESSAGE(STATUS "Compiling with OpenMP support")
  ENDIF(OPENMP_FOUND)
ENDIF(G2O_USE_OPENMP)

GUI

# OpenGL is used in the draw actions for the different types, as well
# as for creating the GUI itself
FIND_PACKAGE(OpenGL)
SET(G2O_USE_OPENGL ON CACHE BOOL "Build g2o with OpenGL support for visualization")
IF (OPENGL_FOUND AND G2O_USE_OPENGL)
  SET (G2O_HAVE_OPENGL 1)
  INCLUDE_DIRECTORIES(${OPENGL_INCLUDE_DIR})
  MESSAGE(STATUS "Compiling with OpenGL support")
ENDIF()

# For building the GUI
FIND_PACKAGE(QGLViewer)

Core Apps and Exampls

# shall we build the core apps using the library
SET(G2O_BUILD_APPS ON CACHE BOOL "Build g2o apps")
IF(G2O_BUILD_APPS)
  MESSAGE(STATUS "Compiling g2o apps")
ENDIF(G2O_BUILD_APPS)

include(CMakeDependentOption)
CMAKE_DEPENDENT_OPTION(G2O_BUILD_LINKED_APPS "Build apps linked with the libraries (no plugin system)" OFF
  "G2O_BUILD_APPS" OFF)

# shall we build the examples
SET(G2O_BUILD_EXAMPLES ON CACHE BOOL "Build g2o examples")
IF(G2O_BUILD_EXAMPLES)
  MESSAGE(STATUS "Compiling g2o examples")
ENDIF(G2O_BUILD_EXAMPLES

gcc編譯器選項

# Compiler specific options for gcc
IF(CMAKE_COMPILER_IS_GNUCXX)
  OPTION (BUILD_WITH_MARCH_NATIVE "Build with \"-march native\"" ON)
  MESSAGE(STATUS "Compiling with GCC")
  
  IF(NOT ${ARCH} MATCHES arm)
    # Generic settings for optimisation
    SET(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -O3 -msse4.2")
    SET(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} -O3 -msse4.2")
  ENDIF()
  # switch off optimization for debug builds
  SET(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -O0")
  SET(CMAKE_C_FLAGS_DEBUG "${CMAKE_C_FLAGS_DEBUG} -O0")

  # OS X
  #IF(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
    #SET(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE}") 
    #SET(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE}") 
  #ENDIF(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
  # Linux
  IF(BUILD_WITH_MARCH_NATIVE AND NOT ${ARCH} MATCHES arm AND ${CMAKE_SYSTEM_NAME} MATCHES "Linux")
    SET(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -march=native")
    SET(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} -march=native")
  ENDIF()
  # activate warnings !!!
  SET(g2o_C_FLAGS "${g2o_C_FLAGS} -Wall -W")
  SET(g2o_CXX_FLAGS "${g2o_CXX_FLAGS} -Wall -W")
ENDIF(CMAKE_COMPILER_IS_GNUCXX)

編譯器對C11的支持

# C++11 support
IF(NOT MSVC)
  include(CheckCXXCompilerFlag)
  CHECK_CXX_COMPILER_FLAG("-std=c++11" COMPILER_SUPPORTS_CXX11)
  CHECK_CXX_COMPILER_FLAG("-std=c++0x" COMPILER_SUPPORTS_CXX0X)
  if(COMPILER_SUPPORTS_CXX11)
    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
  elseif(COMPILER_SUPPORTS_CXX0X)
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++0x")
  else()
    message(STATUS "The compiler ${CMAKE_CXX_COMPILER} has no C++11 support. Please use a different C++ compiler.")
  endif()
endif()

編譯器的編譯條件設置

# specifying compiler flags
SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${g2o_CXX_FLAGS}")
SET(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${g2o_C_FLAGS}")

Eigen3的路徑設置

# Find Eigen3
SET(EIGEN3_INCLUDE_DIR ${G2O_EIGEN3_INCLUDE})
FIND_PACKAGE(Eigen3)
IF(EIGEN3_FOUND)
  SET(G2O_EIGEN3_INCLUDE ${EIGEN3_INCLUDE_DIR} CACHE PATH "Directory of Eigen3")
ELSE(EIGEN3_FOUND)
  SET(G2O_EIGEN3_INCLUDE "" CACHE PATH "Directory of Eigen3")
ENDIF(EIGEN3_FOUND)

頭文件路徑設置

# Set up the top-level include directories
INCLUDE_DIRECTORIES(${g2o_SOURCE_DIR} ${G2O_EIGEN3_INCLUDE})

生成配置文件和添加子文件夾

# Generate config.h
SET(G2O_OPENGL_FOUND ${OPENGL_FOUND})
SET(G2O_HAVE_CHOLMOD ${CHOLMOD_FOUND})
SET(G2O_HAVE_CSPARSE ${CSPARSE_FOUND})
SET(G2O_SHARED_LIBS ${BUILD_SHARED_LIBS})
SET(G2O_LGPL_SHARED_LIBS ${BUILD_LGPL_SHARED_LIBS})
SET(G2O_CXX_COMPILER "${CMAKE_CXX_COMPILER_ID} ${CMAKE_CXX_COMPILER}")
configure_file(config.h.in ${PROJECT_BINARY_DIR}/g2o/config.h)
include_directories(${PROJECT_BINARY_DIR})
INSTALL(FILES ${PROJECT_BINARY_DIR}/g2o/config.h DESTINATION ${CMAKE_INSTALL_PREFIX}/include/g2o)

# Include the subdirectories
ADD_SUBDIRECTORY(EXTERNAL)
ADD_SUBDIRECTORY(g2o)

g2o CMakeLists.txt