问题描述
限时送ChatGPT账号..我使用 CMake (3.4.1) 根据 Boost 库构建了一个 C++ 项目.主机平台是Linux,目标是主机和交叉构建 Android NDK.
I build a C++ project depending on the Boost library using CMake (3.4.1). Host platform is Linux, targets are that host and cross-build Android NDK.
我只使用 Boost 头文件,我刚刚下载/提取了 boost 文件夹(我没有 /usr/include/boost
目录).
I'm only using Boost header files and I just downloaded/extracted the boost folder (and I don't have a /usr/include/boost
directory).
在我的 CMakeLists.txt
文件中,我像这样声明了对 Boost 的依赖:
In my CMakeLists.txt
file I declare the dependency to Boost like this:
find_package(Boost 1.57 REQUIRED)
我像这样配置我的构建:
And I configure my build like this:
BOOST_ROOT=/path/to/boost cmake ../src
对于我的本机构建,它实际上工作.
Which actually works as expected for my native build.
当我现在以完全相同的方式配置构建(仅指定更多环境变量和 CMAKE_TOOLCHAIN_FILE)时,CMake 给了我:
When I now configure a build exactly the same way (only specifying some more environment variables and a CMAKE_TOOLCHAIN_FILE) CMake gives me:
BOOST_ROOT=/path/to/boost JAVA_HOME=/bla/bla/bla
ANDROID_NDK=/bla/bla/bla
ANDROID_SDK=/bla/bla/bla
ANT=/usr/bin/ant
cmake ../src -DCMAKE_TOOLCHAIN_FILE=/bla/bla/android.toolchain.cmake
CMake Error at /usr/share/cmake/Modules/FindBoost.cmake:1247 (message):
Unable to find the requested Boost libraries.
Unable to find the Boost header files. Please set BOOST_ROOT to the root
directory containing Boost or BOOST_INCLUDEDIR to the directory containing
Boost's headers.
Call Stack (most recent call first):
CMakeLists.txt:4 (find_package)
所以我相信我为 Android 目标做了几乎相同的构建,但是为主机构建找到 Boost 的完全相同的方法在这里不起作用.
So I believe I did almost the same to build for the Android target but the very same method that finds Boost for the host-build doesn't work here.
我尝试设置 Boost_DIR
、BOOSTROOT
和 BOOST_INCLUDEDIR
都具有相同的效果.此外,在尝试任何新内容之前,我已经删除了构建目录中的所有内容.
I tried to set Boost_DIR
, BOOSTROOT
and BOOST_INCLUDEDIR
all with the same effect. Also I've deleted all content in the build directory before trying anything new.
这种行为的可能原因是什么?我已经尝试在 FindBoost.cmake
脚本中直接打印 BOOST_ROOT
,如下所示:
What can be possible reasons for this behavior? I've already tried to print BOOST_ROOT
directly in the FindBoost.cmake
script like this:
message("BOOST_ROOT: $ENV{BOOST_ROOT}")
具有预期的行为(编写 BOOST_ROOT:/path/to/boost
).
With the expected behavior (writing BOOST_ROOT: /path/to/boost
).
当然我现在可以作弊,只需将 boost
文件夹链接到交叉编译器的 include
文件夹中,但这当然不好,我想知道是什么继续.
Of course I can cheat now and just link the boost
folder into the include
folder of the cross compiler but that's not nice of course and I want to find out what's going on.
推荐答案
交叉编译时,工具链文件通常设置变量 CMAKE_FIND_ROOT_PATH.结合 CMAKE_FIND_ROOT_PATH_MODE_LIBRARY 变量设置为 ONLY
,CMAKE_FIND_ROOT_PATH
变量用作 find_library
调用的有效 chroot,因此只有给定前缀下的库是搜索.
When cross-compiling, the toolchain file normally sets the variable CMAKE_FIND_ROOT_PATH. Combined with the CMAKE_FIND_ROOT_PATH_MODE_LIBRARY variable set to ONLY
, CMAKE_FIND_ROOT_PATH
variable is used as effective chroot for find_library
calls, so only libraries under the given prefix(es) are searched.
模拟变量的存在是为了调整 find_path
(用于搜索包含路径)和 find_program
的行为.
Analogue variables exist to adjust the behavior for find_path
(used for searching include paths) and find_program
.
您使用的工具链文件实际上在 CMAKE_FIND_ROOT_PATH.cmake#L1521" rel="nofollow noreferrer">第 1521 行:
THe toolchain file you use actually sets CMAKE_FIND_ROOT_PATH
at line 1521:
set( CMAKE_FIND_ROOT_PATH "${ANDROID_TOOLCHAIN_ROOT}/bin"
"${ANDROID_TOOLCHAIN_ROOT}/${ANDROID_TOOLCHAIN_MACHINE_NAME}"
"${ANDROID_SYSROOT}"
"${CMAKE_INSTALL_PREFIX}"
"${CMAKE_INSTALL_PREFIX}/share" )
及以下将 CMAKE_FIND_ROOT_PATH_MODE_*
变量设置为 ONLY
.所以你需要在这些目录之一下安装 Boost,并给出相关的提示(如 BOOST_ROOT).
and below sets CMAKE_FIND_ROOT_PATH_MODE_*
variables to ONLY
. So you need to have Boost installed under one of these directories, and give hints (like BOOST_ROOT) relative to it.
请注意,Boost 应该是为目标平台(在您的情况下为 Android NDK)构建的,而不是为您交叉编译的平台(Linux)构建的.
Note, that Boost should be built for the target platform (Android NDK in you case), not for the platform where you cross-compile (Linux).
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