Where To Download Cmake
Niccoletta Vullo
The command operates in two modes: Module mode and Configmode. In Module mode, the command searches for afind module: a file namedFind.cmake. It looks first in the CMAKE_MODULE_PATHand then in the CMake installation. If a find module is found, it is loaded tosearch for individual components of the package. Find modules containpackage-specific knowledge of the libraries and other files they expect tofind, and internally use commands like find_library to locatethem. CMake provides find modules for many common packages; see thecmake-modules(7) manual.
The Config mode of find_package provides a powerfulalternative through cooperation with the package to be found. Itenters this mode after failing to locate a find module or whenexplicitly requested by the caller. In Config mode the commandsearches for a package configuration file: a file namedConfig.cmake or -config.cmake which isprovided by the package to be found. Given the name of a package, thefind_package command knows how to search deep inside installationprefixes for locations like:
(see documentation of the find_package command for acomplete list of locations). CMake creates a cache entry called_DIR to store the location found or allow the user toset it. Since a package configuration file comes with an installationof its package, it knows exactly where to find everything provided bythe installation. Once the find_package command locates the fileit provides the locations of package components without any additionalsearching.
The [version] option asks find_package to locate aparticular version of the package. In Module mode, the command passesthe request on to the find module. In Config mode the command looksnext to each candidate package configuration file for a packageversion file: a file named ConfigVersion.cmake or-config-.cmake. The version file is loaded totest whether the package version is an acceptable match for theversion requested (see documentation of find_package for theversion file API specification). If the version file claimscompatibility, the configuration file is accepted, or is otherwiseignored. This approach allows each project to define its own rules forversion compatibility.
Each Find.cmake module defines a set of variables that willallow a project to use the software package once it is found. Thosevariables all start with the name of the software being found. With CMake we have tried to establish a convention for namingthese variables, but you should read the comments at the top of themodule for a more definitive answer. The following variables are usedby convention when needed:
Not all of the variables are present in each of the FindXX.cmakefiles. However, the _FOUND should exist under mostcircumstances. If is a library, then _LIBRARIESshould also be defined, and _INCLUDE_DIR should usually bedefined.
If the project converts over to CMake for its build system, thefind_package will still work if the package provides aConfig.cmake file. How to create a CMake package is describedlater in this chapter.
After installation, the configured package configuration filegromit-config.cmake knows the locations of other installed filesrelative to itself. The corresponding package version file isconfigured from its input file gromit-config-version.cmake.in,which contains code such as:
The call to find_package locates an installation of Gromit orterminates with an error message if none can be found (due toREQUIRED). After the command succeeds, the Gromit packageconfiguration file gromit-config.cmake has been loaded, so Gromittargets have been imported and variables like gromit_INCLUDE_DIRShave been defined.
The package configuration file gromit-config.cmake placed in thebuild tree provides the same information to an outside project as thatin the install tree, but refers to files in the source and buildtrees. It shares an identical package version filegromit-config-version.cmake which is placed in the install tree.
CMake provides two central locations to registerpackages that have been built or installed anywhere on a system: aUser Package Registry and a System Package Registry. Thefind_package command searches the two package registries as two ofthe search steps specified in its documentation. The registries areespecially useful for helping projects find packages in non-standardinstall locations or directly in the package build trees. A projectmay populate either the user or system registry (using its own means)to refer to its location. In either case, the package should store apackage configuration file at the registered location and optionally apackage version file earlier in this chapter.
as a REG_SZ value with arbitrary name that specifies the directorycontaining the package configuration file. On UNIX platforms, the userpackage registry is stored in the user home directory under/.cmake/packages. A may appear under the directory
There are two main directories CMake uses when building a project: the sourcedirectory and the binary directory. The source directory is where the sourcecode for the project is located. This is also where the CMakeLists files will befound. The binary directory is sometimes referred to as the build directory andis where CMake will put the resulting object files, libraries, and executables.CMake will not write any files to the source directory, only to the binarydirectory.
Out-of-source builds, where the source and binary directories are different,are strongly encouraged. In-source builds where the source and binarydirectories are the same are supported but should be avoided if possible.Out-of-source builds make it very easy to maintain a clean source tree andallow quick removal of all of the files generated by a build. Having thebuild tree differ from the source tree also makes it easy to support havingmultiple builds of a single source tree. This is useful when you want to havemultiple builds with different options but just one copy of the source code.
The first line of the top level CMakeLists file should always becmake_minimum_required. This allows projects to require a givenversion of CMake and, in addition, allows CMake to be backwards compatible.
For each directory in a project where the CMakeLists.txt file invokesthe project command, CMake generates a top-level Makefile or IDEproject file. The project will contain all targets that are in theCMakeLists.txt file and any subdirectories, as specified by theadd_subdirectory command. If the EXCLUDE_FROM_ALL optionis used in the add_subdirectory command, the generated project willnot appear in the top-level Makefile or IDE project file; this isuseful for generating sub-projects that do not make sense as part ofthe main build process. Consider that a project with a number ofexamples could use this feature to generate the build files for eachexample with one run of CMake, but not have the examples built as partof the normal build process.
CMake includes a Qt-based user interface that can be used on mostplatforms, including UNIX, Mac OS X, and Windows. Thecmake-gui is included in the CMake source code, butyou will need an installation of Qt on your system in order to build it.
On Windows, the executable is named cmake-gui.exe and it should bein your Start menu under Program Files. There may also be a shortcuton your desktop, or if you built CMake from the source, it will be inthe build directory. For UNIX and Mac users, the executable is namedcmake-gui and it can be found where you installed the CMakeexecutables. A GUI will appear similar to what is shown in Figure1. The top two fields are the source codeand binary directories. They allow you to specify where the sourcecode is located for what you want to compile, and where the resultingbinaries should be placed. You should set these two values first. Ifthe binary directory you specify does not exist, it will be createdfor you. If the binary directory has been configured by CMake before,it will then automatically set the source tree.
On most UNIX platforms, if the curses library is supported, CMakeprovides an executable called ccmake. This interface is aterminal-based text application that is very similar to thecmake-gui. To run ccmake, changedirectories into the directory where you want the binaries to be placed. Thenrun ccmake with the path to the source directory on thecommand line. This will start the text interface as shown in Figure2.
From the command line, the cmake executable can be usedto generate a project buildsystem. This is best suited for projects with fewor no options. For larger projects like VTK, using ccmake, or the cmake-gui is recommended. Tobuild a project with cmake, first create and changedirectory to where you want the binaries to be placed. Runcmake specifying the path to the source tree and pass inany options using the -D flag. Unlike ccmake, or thecmake-gui, the configure and generate steps arecombined into one when using the cmake executable.
If Boost was built using the boost-cmake project or from Boost 1.70.0 onit provides a package configuration file for use with find_package's config mode.This module looks for the package configuration file calledBoostConfig.cmake or boost-config.cmake and stores the result inCACHE entry Boost_DIR. If found, the package configuration file is loadedand this module returns with no further action. See documentation ofthe Boost CMake package configuration for details on what it provides.
I'm trying to install rviz from source. It seems a lot of packages are missing from my installation of ROS from source. So, I worked my way through the github repository, cloned the corresponding folders, copied them into /opt/ros/..., and ran cmake to build the packages from source. This worked fine until the package "genpy" where cmake gives the following error:
The problem you're running into is very generic. The catkinConfig.cmake is not on your CMAKE_PREFIX_PATH. The question is why it's not on your path. The only way to know that is to have enough information to reproduce the problem you are having exactly, since it's likely a procedural error.
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