Edit: The accepted answer actually shows that it is pretty normally possible to set CMAKE_MODULE_PATH as any other CMake variable e.g. via the -DCMAKE_MODULE_PATH path CLI parameter. It seems that in my case there is some included CMake script that calls set(CMAKE_MODULE_PATH /library_path), which erases all previous paths set to the variable. That's why I couldn't get the variable to do what I wanted it to do. I'll leave the question here in case anybody else faces this kind of situation.
I'm building a (3rd party) project that uses the Protobuf library (but this question is general). My system has a system-wide install of a newer version of Protobuf than the project is compatible with. So I've downloaded and compiled from source an older version of Protobuf.
The project uses CMake, and in its CMakeLists.txt, there is:
find_package(Protobuf REQUIRED)
Which, however, finds the (incompatible) system install. Of course, CMake doesn't know about my custom build of Protobuf. But how do I tell it?
I've created a FindProtobuf.cmake file in, say, ~/usr/share/cmake-3.0/Modules/ and want the build process to use this one for finding Protobuf. But I haven't succeeded forcing CMake to pick up this one and not the system one. I think the reason is quite obvious from the CMake docs of find_package:
The command has two modes by which it searches for packages: “Module” mode and “Config” mode. Module mode is available when the command is invoked with the above reduced signature. CMake searches for a file called Find<package>.cmake in the CMAKE_MODULE_PATH followed by the CMake installation. If the file is found, it is read and processed by CMake. ... If no module is found and the MODULE option is not given the command proceeds to Config mode.
So until I succeed to change CMAKE_MODULE_PATH, CMake will just pick up the FindProtobuf.cmake installed to the default system path and won't ever proceed to the "Config" mode where I could probably make use of CMAKE_PREFIX_PATH.
It's important for me to not edit the CMakeLists.txt since it belongs to a 3rd party project I don't maintain.
What I've tried (all without success):
calling CMAKE_MODULE_PATH=~/usr/share/cmake-3.0/Modules cmake ... (the env. variable is not "transferred" to the CMake variable with the same name)
calling cmake -DCMAKE_MODULE_PATH=~/usr/share/cmake-3.0/Modules ... (doesn't work, probably by design?)
calling Protobuf_DIR=path/to/my/protobuf cmake ... (the project doesn't support this kind of override for Protobuf)
It seems to me that, unfortunately, the only way to alter the CMAKE_MODULE_PATH used by find_package is to alter it from within CMakeLists.txt, which is exactly what I want to avoid.
Do you have any ideas/workarounds on how not to touch the CMakeLists.txt and still convince find_package to find my custom Protobuf?
For reference, the CMake part of this project is on github .
As a direct answer to your question, yes, you can set CMAKE_MODULE_PATH at the command line by running cmake -DCMAKE_MODULE_PATH=/some/path -S /path/to/src -B /path/to/build.
But that probably doesn't do what you want it to do; see below.
The Bitbucket link you supplied is dead, but here are a few suggestions that might help.
Avoid writing your own find modules, especially when the upstream supplies CMake config modules.
You can direct CMake to your custom Protobuf installation by setting one of CMAKE_PREFIX_PATH or Protobuf_ROOT (v3.12+) to the Protobuf install root.
You can tell find_package to try CONFIG mode first by setting CMAKE_FIND_PACKAGE_PREFER_CONFIG to true (v3.15+). Then set Protobuf_DIR to the directory containing ProtobufConfig.cmake.
Failing all else, you can manually set the variables documented in CMake's own FindProtobuf module, here: https://cmake.org/cmake/help/latest/module/FindProtobuf.html
All these variables can be set at the configure command line with the -D flag.
There are very few environment variables that populate CMake variables to start and I would avoid relying on them. There is an exhaustive list here: https://cmake.org/cmake/help/latest/manual/cmake-env-variables.7.html. CMAKE_MODULE_PATH is not among them.
Related
I am creating a library which I am building and installing with CMake. In the CMakeLists.txt is install(TARGETS mylib ...) to install the library itself and install(EXPORT ...) to create a CMake config. The CMake config means that the library can be found with find_package() by applications wanting to use the library from their own CMakeLists.txt. So far, nothing surprising.
But in addition to that I have useful_fn.cmake that contains a useful CMake function that I want to make available to the applications' CMakeLists.txt. I can install it manually with install install(FILE useful_fn.cmake), but how will the applications know where to find it? Can it be referenced from the config?
Even better, could the CMake config include the installed version directly? So merely running find_package(mylib) provides access to this CMake function? I could do this if I wrote my whole mylib-config.cmake by hand, rather than than getting CMake to generate it like it currently does, but I would really rather not do that just so that I can add one line (include(.../usefulfn.cmake)).
It is misconception that CMake should generate XXXConfig.cmake script. As opposite, intended behavior that CMake generates every other script (names can be any):
XXXConfigTargets.cmake with install(EXPORT)
XXXConfigVersion.cmake with write_basic_package_version_file()
and these scripts are included in the XXXConfig.cmake script written by hands, where you may define additional things:
# File: XXXConfig.cmake
include(${CMAKE_CURRENT_LIST_DIR}/XXXConfigVersion.cmake)
include(${CMAKE_CURRENT_LIST_DIR}/XXXConfigTargets.cmake)
# Here you may provide additional functions and other things.
function(my_func)
...
endfunction()
See more in the CMake packaging documentation.
To clarify further, there is a module that helps your configure valid and relocatable config file.
See macro configure_package_config_file provided by CMakePackageConfigHelpers module.
As mentioned by #Tsyvarev, the XXXConfig.cmake file should still be written by hand but configured with configure_package_config_file instead of configure_file.
I have been trying to build Mozilla RR on a Linux box at work using CMake. We have a slightly eccentric arrangement where shared libraries are stored on network drives in locations like /sw/external/product-name/linux64_g63.dll/. Further, I have built some dependencies for the project in $HOME/sw/. (I am not a sudoer on this box.)
I am rather baffled as how I am supposed to communicate to CMake to look in non-standard directories. So far I have fudged:
PKG_CONFIG_PATH=$HOME/sw/capnproto-0.6.1/lib/pkconfig \
CC=gcc-6.3 CXX=g++-6.3 \
cmake \
-DCMAKE_INSTALL_PREFIX=$HOME/sw/rr-5.1.0 \
-DPYTHON_EXECUTABLE=$HOME/bin/python2 \
-DCMAKE_FIND_ROOT_PATH=$HOME/sw/libseccomp-2.2.3/ \
../src/
Which is obviously not a scalable solution, but it does at least complete the configuration successfully and emit some Makefiles.
If I omit -DCMAKE_FIND_ROOT_PATH=$HOME/sw/libseccomp-2.2.3/, CMake fails, complaining about a missing libseccomp-2.2.3 dependency. But it works if I do have that definition, telling me that CMake understands where the libseccomp-2.2.3 files are and so will properly add the paths to the necessary compiler invocations.
However, make does not succeed, because gcc fails to find a required header file from the libseccomp probject. Examining make VERBOSE=1, I find that CMake hasn't added -I$HOME/sw/libseccomp-2.2.3/include to the gcc invocation.
I feel like this is not the right approach. The other answers I have looked at tell me to modify the CMakeLists.txt file, but surely
that is not going to be scalable across multiple CMake projects, and
for each project, that will need me to maintain a separate CMakeLists.txt file for every platform (Solaris/Linux/Darwin/Cygwin) I build the software on.
Is there a canonical solution to solving this problem? Perhaps a per-site configuration file that will tell CMake how to find libraries and headers, for all projects I build on that site?
Your approach is correct, but cmake is never told to include SECCOMP - see end of this post.
The way cmake can be informed about custom dependency directory depends on how the dependency is searched (i.e. on what is written in CMakeLists.txt).
find_package/find_library/find_path/find_program
If dependency is found with one of above-mentioned commands, custom search directories can be easily added with CMAKE_PREFIX_PATH. There is no need to add full path to include, lib or bin - when package root is added find_-command will check appropriate sub-directories. CMAKE_PREFIX_PATH can be also set with environment variable.
Second option is CMAKE_FIND_ROOT_PATH. Every path added to CMAKE_FIND_ROOT_PATH list treated as separate root directory and is searched before system root directory.
Note that CMAKE_FIND_ROOT_PATH will be ignored by find_-commands with NO_CMAKE_FIND_ROOT_PATH argument.
Following four variables may be used to tune the usage of CMAKE_FIND_ROOT_PATH:
CMAKE_FIND_ROOT_PATH_MODE_PACKAGE
CMAKE_FIND_ROOT_PATH_MODE_INCLUDE
CMAKE_FIND_ROOT_PATH_MODE_LIBRARY
CMAKE_FIND_ROOT_PATH_MODE_PROGRAM
When use of host system default libraries is undesired setting CMAKE_FIND_ROOT_PATH_MODE_INCLUDE and CMAKE_FIND_ROOT_PATH_MODE_LIBRARY to ONLY is a good practice. If dependency library or header is not found in CMAKE_FIND_ROOT_PATH the configuration will fail. If cmake is allowed search system paths too, it is most likely that errors will occur during linking step or even runtime.
See find_package docs for more details.
find_package only
All above applies to find_package command too.
find_package can operate in two modes MODULE and CONFIG.
In MODULE mode cmake uses Find[PackageName].cmake script (module) to find dependent package. CMake comes with large number of modules and custom modules can be added with CMAKE_MODULE_PATH variable. Often find-modules can be informed about custom search paths via environment or cmake variables.
E.g. FindGTest.cmake searches path stored in GTEST_ROOT variable.
If no find module is available, find_package enters CONFIG mode. If a dependency package provides [PackageName]Config.cmake or [LowercasePackageName]-config.cmake cmake can be easily informed about that package with [PackageName]_DIR variable.
Example:
CMakeLists.txt contains:
find_package(Qt5)
FindQt5.cmake is not available, but ~/Qt5/Qt5.8/lib/cmake/Qt5Config.cmake file exists, so add
-DQt5_DIR="${HOME}/Qt5/Qt5.8/lib/cmake"
to cmake call.
pkg-config
CMake can use information provided by external pkg-config tool. It is usually done with pkg_check_modules command. Directory used by pkg-config can be customized with PKG_CONFIG_PATH environment variable. According to cmake documentation instead of setting PKG_CONFIG_PATH, custom .pc-files directories can be added via CMAKE_PREFIX_PATH. If CMake version is pre-3.1, PKG_CONFIG_USE_CMAKE_PREFIX_PATH have to be set to TRUE(ON) to enable this feature.
Methods of customizing dependencies search path is defined by CMakeLists.txt content. There is no universal solution here.
And now back to missing SECCOMP headers...
In CMakeLists.txt SECCOMP header is found with
find_path(SECCOMP NAMES "linux/seccomp.h")
but I cannot find any command telling CMake to use the found header. For example:
target_include_directories(<target_name> ${SECCOMP})
or globally:
include_directories(${SECCOMP})
I belive that CMakeLists.txt should be fixed. It is not a platform dependent solution.
I have a project which builds for PPC, the Toolchain is working correctly, i can build when the sysroot is installed under /opt/poky/1.5. Now i tried to move that Installation to the Project Directory (it is not a part of the Repository there, it is just installed there so it is not reliant on that fix path, so that everyone can check out the project and build it wothout setting up the sysroot under that fixed folder).
To achieve this I set CMAKE_SYSROOT to "${PROJECT_SOURCE_DIR}/poky" where the poky will be installed upon execution of a custom build script (the project also needs to build a secure image, so it is way simpler to use a build script instead of anything else, also this is convenient for jenkins).
Since the CMAKE_SYSROOT is build from the PROJECT_SOURCE_DIR which is different for the CMakeTestCCompiler Project, the cmake call fails teloling me that the CCompiler is broken of course. So I want to know, how I am supposed to get the CMakeTestCCompiler Project to compile with the same CMAKE_SYSROOT variable, without altering the CMakeTestCCompiler Project itself (of course).
Somehow I cannot find an answer anywhere, it seems that noone ever had this issue (which frankly i cannot understand, this should be a common setup in my opinion). (Or maybe i am just too much of a noob when it comes to CMAKE, which i will gladly admit)
I am not interested in solutions like: "JUST INSTALL IT IN A FIX PATH" or such... please, I need the setup like this, I have reasons for that.
THX for reading/trying/answering/helping
Have a nice day
EDIT1:
In CMakeLists.txt (top level CMakeFile so it should be used by any build):
`SET(CMAKE_SYSROOT "${PROJECT_SOURCE_DIR}/poky/sysroots")`
In ToolchainCMake (the one given to the cmake as CMAKE_TOOLCHAIN_FILE):
`SET(CMAKE_SYSTEM_NAME Linux)`
`SET(CMAKE_SYSTEM_VERSION 1)`
`SET(CMAKE_SYSROOT "${PROJECT_SOURCE_DIR}/poky/sysroots")`
`SET(COMPILER_ROOT ${PROJECT_SOURCE_DIR}/poky/sysroots/i686-pokysdk-linux/usr/bin/powerpc-poky-linux-gnuspe)`
`SET(CMAKE_C_COMPILER ${COMPILER_ROOT}/powerpc-poky-linux-gnuspe-gcc)`
`SET(CMAKE_CXX_COMPILER ${COMPILER_ROOT}/powerpc-poky-linux-gnuspe-g++)`
`MESSAGE("CMAKE_C_COMPILER: ${CMAKE_C_COMPILER}")`
`MESSAGE("CMAKE_CXX_COMPILER: ${CMAKE_CXX_COMPILER}")`
`MESSAGE("COMPILER_ROOT: ${COMPILER_ROOT}")`
`SET(CMAKE_FIND_ROOT_PATH ${SYS_ROOT}/ppce500v2-poky-linux-gnuspe)`
`SET(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)`
`SET(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)`
`SET(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)`
EDIT2:
I used the
`set(CMAKE_C_COMPILER_WORKS 1 CACHE INTERNAL "")`
`set(CMAKE_CXX_COMPILER_WORKS 1 CACHE INTERNAL "")`
settings to simulate the CMakeTestCCompiler build succeeding and realized that I am facing some additional problems: It seem that the packages are looked up on the system instead of the CMAKE_SYSROOT folder. Even tried the
`SET(CMAKE_FIND_ROOT_PATH ${CMAKE_SYSROOT})`
to try to force the search in there, but without luck. In the CMakeError.log I can see, that the compiler itself was configured with the prefix option that points to /opt/poky/1.5, the path that i want to "overwrite", now I am not sure if the compiler could even deal with an alternate path.
I felt the need to add these information, they not really add to the problem at hand.
ERRORS:
I also found some errors in the above cmake:
`SET(CMAKE_SYSROOT "${PROJECT_SOURCE_DIR}/poky/sysroots")`
must be
`SET(CMAKE_SYSROOT "${PROJECT_SOURCE_DIR}/poky/sysroots/ppce500v2-poky-linux-gnuspe")`
instead and therefor the
`SET(CMAKE_FIND_ROOT_PATH ${SYS_ROOT}/ppce500v2-poky-linux-gnuspe)`
changes to
`SET(CMAKE_FIND_ROOT_PATH ${CMAKE_SYSROOT})`
EDIT: Whole answer changed.
My first suspicion was that the problem is that value of ${PROJECT_SOURCE_DIR} is not known in CMAKE_TOOLCHAIN_FILE as it is processed before CMakeLists.txt. But this isn't true.
I had similar problem (CMake 2.8.12.2), everything worked OK, when I passed cross compiler by CC environment variable with --sysroot option, i.e. CMake was invoked as follows:
CC="arm-linux-gnueabi-gcc --sysroot=/path/to/sysroot" cmake /path/to/sources
When I switched to using toolchain file, CMake started to report that C compiler doesn't work.
To workaround this problem, I use CMakeForceCompiler package. Parts toolchain file (along with comments) I think are relevant:
include(CMakeForceCompiler)
set(CMAKE_SYSTEM_NAME Linux)
set(CMAKE_SYSTEM_VERSION 1)
# Force compiler - only option that actually works
cmake_force_c_compiler (${TOOLCHAIN_PATH}/bin/arm-linux-gnueabi-gcc GNU)
cmake_force_cxx_compiler(${TOOLCHAIN_PATH}/bin/arm-linux-gnueabi-g++ GNU)
# NOTE: CMAKE_SYSROOT doesn't work as expected
add_definitions("--sysroot=${TOOLCHAIN_SYSROOT}")
set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} --sysroot=${TOOLCHAIN_SYSROOT}" CACHE INTERNAL "" FORCE)
Note, that TOOLCHAIN_PATH and TOOLCHAIN_SYSROOT are my local variables set before.
I want to use some third-party headers (or a library) in a project that uses CMake. But it does not find the headers (the library). Why does CMake not find it?
CMake's find routines look for headers and libraries at some specific places. This includes the PATH variable, and the default locations for installed software, e.g., for many Linuces /usr/bin. Additionally, it evaluates the CMake variable CMAKE_PREFIX_PATH.
You have two possibilities to help CMake finding the required files:
Check whether your software is properly installed. For self-compiled software, that's usually done by make install or similar. If you use packages (RPM or deb), they are in general installed and can be found with the PATH variable.
If you don't want or can install the software, add its path to the CMAKE_PREFIX_PATH variable. Either pass it to the CMake call cmake -DCMAKE_PREFIX_PATH=/path/to/software .. or edit/add the according field in the CMake-GUI.
You have to delete the CMakeCache.txt, otherwise CMake will not find the library, because it does not check but use the cached result. Re-run CMake and it should work.
Evaluation order
If you have multiple versions of a library on your system, add the one you want to use to the CMAKE_PREFIX_PATH as the variables gets evaluated prior to the system path variables.
Module-specific variables
Some modules offer specific variables like mylib_DIR or mylib_ROOT to indicate the search path. Its use is discouraged and they are only left for backwards-compatibility. New modules don't have these modules and commits adding such variables are rejected by the CMake developers.
Documentation
More details on how CMake searches files and in which order can be found in the documentation: https://cmake.org/cmake/help/latest/command/find_library.html
I am porting some code over to windows and my cmake checks for the package Libavahi using
find_package(Libavahi)
I have the headers, dll, etc. but I'm not sure where to place these such that cmake will find them.
Where can I put these files to be found by cmake? They're in a folder called usr.
I see that the module path is specified using:
set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_SOURCE_DIR}/cmake/Modules/")
but I'm wondering if there is a default location that will be searched as well
The CMake manual fully specifies the rather complicated search order for the different find_* commands. Unfortunately, since Windows lacks a default directory structure à la /usr/local/lib, it is hard to come up with reasonable defaults here.
One of the most reliable ways of managing directories is through environment variable hints. You simply add an $ENV{MY_VAR} to the HINTS section of the find command and then document that environment variable in your project's readme. Most users that are capable of compiling a C++ program know how to use environment variables, and it is way more convenient than having to give the path on the command line every time (although it never hurts to leave that as an additional option).
For find_package CMake offers a special mechanism on Windows called the package registry. CMake maintains a list of package information in the Windows registry under HKEY_CURRENT_USER\Software\Kitware\CMake\Packages\. Packages build from source can register there using the export command. Other projects build later on the same machine will then be able to find that package without additional configuration. This is quite powerful if you need to build a lot of interdependent projects from source on the same machine.
Update: Starting with version 3.12, CMake now implicitly considers the <PackageName>_Root environment variable a HINT for every find_package call.
In the newer versions of cmake, you can use the --debug-find option to list the directories that cmake is searching through. Somethin like:
cmake -DCMAKE_BUILD_TYPE=Release -DBUILD_TOOLS=ON --debug-find .