1// -*- mode:doc; -*- 2// vim: set syntax=asciidoc: 3 4=== Infrastructure for CMake-based packages 5 6[[cmake-package-tutorial]] 7 8==== +cmake-package+ tutorial 9 10First, let's see how to write a +.mk+ file for a CMake-based package, 11with an example : 12 13------------------------ 1401: ################################################################################ 1502: # 1603: # libfoo 1704: # 1805: ################################################################################ 1906: 2007: LIBFOO_VERSION = 1.0 2108: LIBFOO_SOURCE = libfoo-$(LIBFOO_VERSION).tar.gz 2209: LIBFOO_SITE = http://www.foosoftware.org/download 2310: LIBFOO_INSTALL_STAGING = YES 2411: LIBFOO_INSTALL_TARGET = NO 2512: LIBFOO_CONF_OPTS = -DBUILD_DEMOS=ON 2613: LIBFOO_DEPENDENCIES = libglib2 host-pkgconf 2714: 2815: $(eval $(cmake-package)) 29------------------------ 30 31On line 7, we declare the version of the package. 32 33On line 8 and 9, we declare the name of the tarball (xz-ed tarball recommended) 34and the location of the tarball on the Web. Buildroot will automatically 35download the tarball from this location. 36 37On line 10, we tell Buildroot to install the package to the staging 38directory. The staging directory, located in +output/staging/+ 39is the directory where all the packages are installed, including their 40development files, etc. By default, packages are not installed to the 41staging directory, since usually, only libraries need to be installed in 42the staging directory: their development files are needed to compile 43other libraries or applications depending on them. Also by default, when 44staging installation is enabled, packages are installed in this location 45using the +make install+ command. 46 47On line 11, we tell Buildroot to not install the package to the 48target directory. This directory contains what will become the root 49filesystem running on the target. For purely static libraries, it is 50not necessary to install them in the target directory because they will 51not be used at runtime. By default, target installation is enabled; setting 52this variable to NO is almost never needed. Also by default, packages are 53installed in this location using the +make install+ command. 54 55On line 12, we tell Buildroot to pass custom options to CMake when it is 56configuring the package. 57 58On line 13, we declare our dependencies, so that they are built 59before the build process of our package starts. 60 61Finally, on line line 15, we invoke the +cmake-package+ 62macro that generates all the Makefile rules that actually allows the 63package to be built. 64 65[[cmake-package-reference]] 66 67==== +cmake-package+ reference 68 69The main macro of the CMake package infrastructure is 70+cmake-package+. It is similar to the +generic-package+ macro. The ability to 71have target and host packages is also available, with the 72+host-cmake-package+ macro. 73 74Just like the generic infrastructure, the CMake infrastructure works 75by defining a number of variables before calling the +cmake-package+ 76macro. 77 78First, all the package metadata information variables that exist in 79the generic infrastructure also exist in the CMake infrastructure: 80+LIBFOO_VERSION+, +LIBFOO_SOURCE+, +LIBFOO_PATCH+, +LIBFOO_SITE+, 81+LIBFOO_SUBDIR+, +LIBFOO_DEPENDENCIES+, +LIBFOO_INSTALL_STAGING+, 82+LIBFOO_INSTALL_TARGET+. 83 84A few additional variables, specific to the CMake infrastructure, can 85also be defined. Many of them are only useful in very specific cases, 86typical packages will therefore only use a few of them. 87 88* +LIBFOO_SUBDIR+ may contain the name of a subdirectory inside the 89 package that contains the main CMakeLists.txt file. This is useful, 90 if for example, the main CMakeLists.txt file is not at the root of 91 the tree extracted by the tarball. If +HOST_LIBFOO_SUBDIR+ is not 92 specified, it defaults to +LIBFOO_SUBDIR+. 93 94* +LIBFOO_CONF_ENV+, to specify additional environment variables to 95 pass to CMake. By default, empty. 96 97* +LIBFOO_CONF_OPTS+, to specify additional configure options to pass 98 to CMake. By default, empty. A number of common CMake options are 99 set by the +cmake-package+ infrastructure; so it is normally not 100 necessary to set them in the package's +*.mk+ file unless you want 101 to override them: 102 103** +CMAKE_BUILD_TYPE+ is driven by +BR2_ENABLE_RUNTIME_DEBUG+; 104** +CMAKE_INSTALL_PREFIX+; 105** +BUILD_SHARED_LIBS+ is driven by +BR2_STATIC_LIBS+; 106** +BUILD_DOC+, +BUILD_DOCS+ are disabled; 107** +BUILD_EXAMPLE+, +BUILD_EXAMPLES+ are disabled; 108** +BUILD_TEST+, +BUILD_TESTS+, +BUILD_TESTING+ are disabled. 109 110* +LIBFOO_SUPPORTS_IN_SOURCE_BUILD = NO+ should be set when the package 111 cannot be built inside the source tree but needs a separate build 112 directory. 113 114* +LIBFOO_MAKE+, to specify an alternate +make+ command. This is 115 typically useful when parallel make is enabled in the configuration 116 (using +BR2_JLEVEL+) but that this feature should be disabled for 117 the given package, for one reason or another. By default, set to 118 +$(MAKE)+. If parallel building is not supported by the package, 119 then it should be set to +LIBFOO_MAKE=$(MAKE1)+. 120 121* +LIBFOO_MAKE_ENV+, to specify additional environment variables to 122 pass to make in the build step. These are passed before the +make+ 123 command. By default, empty. 124 125* +LIBFOO_MAKE_OPTS+, to specify additional variables to pass to make 126 in the build step. These are passed after the +make+ command. By 127 default, empty. 128 129* +LIBFOO_INSTALL_OPTS+ contains the make options used to 130 install the package to the host directory. By default, the value 131 is +install+, which is correct for most CMake packages. It is still 132 possible to override it. 133 134* +LIBFOO_INSTALL_STAGING_OPTS+ contains the make options used to 135 install the package to the staging directory. By default, the value 136 is +DESTDIR=$(STAGING_DIR) install/fast+, which is correct for most 137 CMake packages. It is still possible to override it. 138 139* +LIBFOO_INSTALL_TARGET_OPTS+ contains the make options used to 140 install the package to the target directory. By default, the value 141 is +DESTDIR=$(TARGET_DIR) install/fast+. The default value is correct 142 for most CMake packages, but it is still possible to override it if 143 needed. 144 145With the CMake infrastructure, all the steps required to build and 146install the packages are already defined, and they generally work well 147for most CMake-based packages. However, when required, it is still 148possible to customize what is done in any particular step: 149 150* By adding a post-operation hook (after extract, patch, configure, 151 build or install). See xref:hooks[] for details. 152 153* By overriding one of the steps. For example, even if the CMake 154 infrastructure is used, if the package +.mk+ file defines its own 155 +LIBFOO_CONFIGURE_CMDS+ variable, it will be used instead of the 156 default CMake one. However, using this method should be restricted 157 to very specific cases. Do not use it in the general case. 158