C++ 如何将变量传递给cmake脚本

我试图将一个变量传递给cmake脚本，但显然我做得不正确。我正试图通过遵循教程来构建一个chrono项目。下面是我的教程：

CMakeLists.txt修改如下：

#--------------------------------------------------------------
# 
# Example of CMake configuration file to build an external 
# project depending on Chrono and on optional Chrono modules.
# 
# This minimal sample project can be used as a template for a
# user project.  Modify sections 1, 2, and 3 below as appropriate.
# 
#--------------------------------------------------------------
 

cmake_minimum_required(VERSION 2.8)

#--------------------------------------------------------------
# === 1 === 
# Modify the project name if you want: 
#--------------------------------------------------------------

project(my_project)

#--------------------------------------------------------------
# === 2 ===
# Find the Chrono package and any REQUIRED or OPTIONAL modules
# by invoking the find_package function in CONFIG mode:
find_package(Chrono
             COMPONENTS Irrlicht
             CONFIG)

# The following Chrono modules can be requested (their names
# are case insensitive): Cascade, Cosimulation, FEA, Irrlicht,
# Matlab, Parallel, Postprocess, Python, Vehicle.
# 
# Note that you will have to set the variable Chrono_DIR to 
# specify the location of the ChronoConfig.cmake script, if
# it is not in its default install location.
# Chrono_DIR can be either a Chrono build tree or a Chrono install tree.
# 
# The following variables are set and can be used further down:
# CHRONO_FOUND
#   set to true if Chrono and all required components were found
# CHRONO_C_FLAGS
# CHRONO_CXX_FLAGS
#   C and C++ compilation flags
# CHRONO_INCLUDE_DIRS
#   additional paths for included headers
# CHRONO_LIBRARIES
#   list of required libraries (with full path)
# CHRONO_LINKER_FLAGS
#   additional linker flags
# CHRONO_DLLS
#   list of all DLL dependencies (with full path)
# CHRONO_DATA_DIR
#   path to the Chrono data make_directory
# 
# In addition, for each requested component [COMPONENT], the
# following variable is set to true (ON) or false (OFF):
# CHRONO_[COMPONENT]_FOUND
# 
# In this example, we only request the Irrlicht module (required)
#--------------------------------------------------------------
#Chrono_DIR = "/home/richard/chrono_build/lib"

LIST(APPEND CMAKE_PREFIX_PATH "${CMAKE_INSTALL_PREFIX}/../Chrono/lib")
find_package(Chrono
             COMPONENTS Irrlicht
             CONFIG)

#--------------------------------------------------------------
# Return now if Chrono or a required component was not found.
#--------------------------------------------------------------

if (NOT Chrono_FOUND)
  message("Could not find Chrono or one of its required modules")
  return()
endif()

#--------------------------------------------------------------
# Enable creation of "application bundles" on MacOSX.
#--------------------------------------------------------------

# This is necessary for any Irrlicht-based project (like the example here).
# For OpenGL-based or non-graphics projects, this is optional and the block
# below can be removed (or else explcitly set CMAKE_MACOSX_BUNDLE to 'OFF').
#
# If creating application bundles, the build output will be named 'myexe.app'.
# Use the convenience script 'run_app.sh' available under 'contrib/appbundle-macosx/'
# to run:
#     start_demo.sh myexe.app

if(APPLE)
    set(CMAKE_MACOSX_BUNDLE ON)
endif()

#--------------------------------------------------------------
# Add path to Chrono headers and to headers of all dependencies
# of the requested modules.
#--------------------------------------------------------------

include_directories(${CHRONO_INCLUDE_DIRS})

#-----------------------------------------------------------------------------
# Fix for VS 2017 15.8 and newer to handle alignment specification with Eigen
#-----------------------------------------------------------------------------

if(${CMAKE_SYSTEM_NAME} MATCHES "Windows")
  if(MSVC AND ${MSVC_VERSION} GREATER_EQUAL 1915)
    add_definitions( "-D_ENABLE_EXTENDED_ALIGNED_STORAGE" )
  endif()
endif()

#--------------------------------------------------------------
# Tweaks to disable some warnings with MSVC
#--------------------------------------------------------------
if(MSVC)
    add_definitions("-D_CRT_SECURE_NO_DEPRECATE")  # avoids deprecation warnings
    add_definitions("-D_SCL_SECURE_NO_DEPRECATE")  # avoids deprecation warnings
    add_definitions( "-DNOMINMAX" )                # do not use MSVC's min/max macros
    set(EXTRA_COMPILE_FLAGS "/wd4275")             # disable warnings triggered by Irrlicht
else()
    set(EXTRA_COMPILE_FLAGS "")
endif()

#--------------------------------------------------------------
# === 3 ===
# Add the executable from your project and specify all C++ 
# files in your project. 
#--------------------------------------------------------------

add_executable(myexe my_example.cpp)

#--------------------------------------------------------------
# Set properties for your executable target
# 
# Note that here we define a macro CHRONO_DATA_DIR which will
# contain the path to the Chrono data directory, either in its
# source tree (if using a build version of Chrono), or in its
# install tree (if using an installed version of Chrono).
#--------------------------------------------------------------

set_target_properties(myexe PROPERTIES 
        COMPILE_FLAGS "${CHRONO_CXX_FLAGS} ${EXTRA_COMPILE_FLAGS}"
        COMPILE_DEFINITIONS "CHRONO_DATA_DIR=\"${CHRONO_DATA_DIR}\""
        LINK_FLAGS "${CHRONO_LINKER_FLAGS}")

#--------------------------------------------------------------
# Link to Chrono libraries and dependency libraries
#--------------------------------------------------------------

target_link_libraries(myexe ${CHRONO_LIBRARIES})

#--------------------------------------------------------------
# === 4 (OPTIONAL) ===
# 
# Optionally, add a custom command for copying all Chrono and
# dependency DLLs to the appropriate binary output folder.
# This function has effect only on Windows.
# 
# Note that you must first set EXECUTABLE_OUTPUT_PATH
# (this can simply be ${CMAKE_BINARY_DIR}, like in this example)
#--------------------------------------------------------------

set(EXECUTABLE_OUTPUT_PATH ${CMAKE_BINARY_DIR})
add_DLL_copy_command("${CHRONO_DLLS}")

我正在使用Ubuntu20.04，并且正在尝试使用cmake设置构建。我使用的命令是：

cmake -S template_project/ -B build -Chrono_DIR:STRING=/home/richard/chrono_build/lib

我得到的错误是：

home/richard/chrono_build/lib
loading initial cache file hrono_DIR:STRING=/home/richard/chrono_build/lib
CMake Error: Error processing file: /home/richard/Chrono_workspace/hrono_DIR:STRING=/home/richard/chrono_build/lib
-- Could NOT find Chrono (missing: Chrono_DIR)
-- Could NOT find Chrono (missing: Chrono_DIR)
Could not find Chrono or one of its required modules
-- Configuring incomplete, errors occurred!
See also "/home/richard/Chrono_workspace/build/CMakeFiles/CMakeOutput.log".

显然，这不是正确的设置“Chrono_Dir”的方法，因为我会出错。在使用CMake命令时，如何传递该信息，或者需要将其添加到cmakelists.txt文件中？我知道这是一个新手问题，但我被卡住了，希望得到一些帮助。我试着跟踪这个stackoverflow，但我显然不明白发生了什么

编辑：

我尝试了下面的评论/答案：

cmake -S template_project/ -B build -DChrono_DIR=/home/richard/chrono_build/lib

现在输出是：

-- Could NOT find Chrono (missing: Chrono_DIR)
-- Could NOT find Chrono (missing: Chrono_DIR)
Could not find Chrono or one of its required modules
-- Configuring done
-- Generating done
-- Build files have been written to: /home/richard/Chrono_workspace/build

也许你可以试试：

cmake -S template_project/ -B build -DChrono_DIR=/home/richard/chrono_build/lib

cmake-D：创建或更新cmake缓存项

然后您可以在CMakeList.txt中访问它，如下所示：

message("Chrono_DIR=" ${Chrono_DIR})

也许你可以试试：

cmake -S template_project/ -B build -DChrono_DIR=/home/richard/chrono_build/lib

cmake-D：创建或更新cmake缓存项

然后您可以在CMakeList.txt中访问它，如下所示：

message("Chrono_DIR=" ${Chrono_DIR})

---

您忘记了变量名之前的-D。尝试使用cmake-S template_project/-B build--DChrono_DIR:STRING=/home/richard/chrono_build/libtry-DChrono_DIR代替-chrono_DIR@AliRazmkhah有点进一步，但仍然不太工作更新了我的问题上面。Chrono_DIR仍然缺少描述：“Chrono_DIR可以是Chrono构建树或Chrono安装树。”。那么，您为

chrono\u DIR

变量指定的值（

/home/richard/chrono\u build/lib

）是生成树还是安装树？根据目录命名，它闻起来像构建树是

/home/richard/chrono\u build

，您将

chrono\u DIR

设置到它的

lib/

子目录，这与描述相矛盾。@Tsyvarev按照您的建议做了。仍然得到相同的输出。该文档还声明“如果ChronoConfig.cmake脚本不在其默认安装位置，则必须设置变量Chrono_DIR以指定ChronoConfig.cmake脚本的位置。”my Chrono Build中没有ChronoConfig.cmake脚本。。奇怪的我想你还得多上网看看。你忘了变量名前的-D。尝试使用cmake-S template_project/-B build--DChrono_DIR:STRING=/home/richard/chrono_build/libtry-DChrono_DIR代替-chrono_DIR@AliRazmkhah有点进一步，但仍然不太工作更新了我的问题上面。Chrono_DIR仍然缺少描述：“Chrono_DIR可以是Chrono构建树或Chrono安装树。”。那么，您为

chrono\u DIR

变量指定的值（

/home/richard/chrono\u build/lib

）是生成树还是安装树？根据目录命名，它闻起来像构建树是

/home/richard/chrono\u build

，您将

chrono\u DIR

设置到它的

lib/

子目录，这与描述相矛盾。@Tsyvarev按照您的建议做了。仍然得到相同的输出。该文档还声明“如果ChronoConfig.cmake脚本不在其默认安装位置，则必须设置变量Chrono_DIR以指定ChronoConfig.cmake脚本的位置。”my Chrono Build中没有ChronoConfig.cmake脚本。。奇怪的我想我还得在网上多看些东西。我想还得再看一点，但还是不太管用。更新了我上面的问题。Chrono_DIR仍然是missing@Dick这确实解决了你的问题。您的设置有其他问题这一事实与此无关。用您遇到的下一个问题更新问题不是解决此问题的方法。标记为已接受，并为下一道题写一个新问题。每个问题一个问题。有关SO的规则和指导原则的更多信息，请查看。@Dick您可以在CMakeList.txt中访问它，如下所示：消息（“Chrono_DIR=“${Chrono_DIR}”）更进一步，但仍然不太有效更新了我上面的问题。Chrono_DIR仍然是missing@Dick这确实解决了你的问题。您的设置有其他问题这一事实与此无关。用您遇到的下一个问题更新问题不是解决此问题的方法。标记为已接受，并为下一道题写一个新问题。每个问题一个问题。有关SO的规则和指南的更多信息，请查看。@Dick您可以在CMakeList.txt中访问它，如下所示：message（“Chrono_DIR=“${Chrono_DIR}）