142 lines
5.8 KiB
Plaintext
142 lines
5.8 KiB
Plaintext
Infrastructure for CMake-based packages
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---------------------------------------
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[[cmake-package-tutorial]]
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+cmake-package+ tutorial
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~~~~~~~~~~~~~~~~~~~~~~~~
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First, let's see how to write a +.mk+ file for a CMake-based package,
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with an example :
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------------------------
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01: #############################################################
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02: #
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03: # libfoo
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04: #
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05: #############################################################
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06: LIBFOO_VERSION = 1.0
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07: LIBFOO_SOURCE = libfoo-$(LIBFOO_VERSION).tar.gz
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08: LIBFOO_SITE = http://www.foosoftware.org/download
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09: LIBFOO_INSTALL_STAGING = YES
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10: LIBFOO_INSTALL_TARGET = YES
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11: LIBFOO_CONF_OPT = -DBUILD_DEMOS=ON
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12: LIBFOO_DEPENDENCIES = libglib2 host-pkg-config
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13:
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14: $(eval $(cmake-package))
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------------------------
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On line 6, we declare the version of the package.
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On line 7 and 8, we declare the name of the tarball and the location
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of the tarball on the Web. Buildroot will automatically download the
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tarball from this location.
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On line 9, we tell Buildroot to install the package to the staging
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directory. The staging directory, located in +output/staging/+
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is the directory where all the packages are installed, including their
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development files, etc. By default, packages are not installed to the
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staging directory, since usually, only libraries need to be installed in
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the staging directory: their development files are needed to compile
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other libraries or applications depending on them. Also by default, when
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staging installation is enabled, packages are installed in this location
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using the +make install+ command.
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On line 10, we tell Buildroot to also install the package to the
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target directory. This directory contains what will become the root
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filesystem running on the target. Usually, we try not to install header
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files and to install stripped versions of the binary. By default, target
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installation is enabled, so in fact, this line is not strictly
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necessary. Also by default, packages are installed in this location
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using the +make install+ command.
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On line 11, we tell Buildroot to pass custom options to CMake when it is
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configuring the package.
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On line 12, we declare our dependencies, so that they are built
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before the build process of our package starts.
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Finally, on line line 14, we invoke the +cmake-package+
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macro that generates all the Makefile rules that actually allows the
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package to be built.
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[[cmake-package-reference]]
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+cmake-package+ reference
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~~~~~~~~~~~~~~~~~~~~~~~~~
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The main macro of the CMake package infrastructure is
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+cmake-package+. It is similar to the +generic-package+ macro. The ability to
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have target and host packages is also available, with the
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+host-cmake-package+ macro.
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Just like the generic infrastructure, the CMake infrastructure works
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by defining a number of variables before calling the +cmake-package+
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macro.
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First, all the package metadata information variables that exist in
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the generic infrastructure also exist in the CMake infrastructure:
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+LIBFOO_VERSION+, +LIBFOO_SOURCE+, +LIBFOO_PATCH+, +LIBFOO_SITE+,
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+LIBFOO_SUBDIR+, +LIBFOO_DEPENDENCIES+, +LIBFOO_INSTALL_STAGING+,
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+LIBFOO_INSTALL_TARGET+.
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A few additional variables, specific to the CMake infrastructure, can
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also be defined. Many of them are only useful in very specific cases,
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typical packages will therefore only use a few of them.
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* +LIBFOO_SUBDIR+ may contain the name of a subdirectory inside the
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package that contains the main CMakeLists.txt file. This is useful,
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if for example, the main CMakeLists.txt file is not at the root of
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the tree extracted by the tarball. If +HOST_LIBFOO_SUBDIR+ is not
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specified, it defaults to +LIBFOO_SUBDIR+.
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* +LIBFOO_CONF_ENV+, to specify additional environment variables to
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pass to CMake. By default, empty.
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* +LIBFOO_CONF_OPT+, to specify additional configure options to pass
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to CMake. By default, empty.
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* +LIBFOO_MAKE+, to specify an alternate +make+ command. This is
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typically useful when parallel make is enabled in the configuration
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(using +BR2_JLEVEL+) but that this feature should be disabled for
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the given package, for one reason or another. By default, set to
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+$(MAKE)+. If parallel building is not supported by the package,
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then it should be set to +LIBFOO_MAKE=$(MAKE1)+.
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* +LIBFOO_MAKE_ENV+, to specify additional environment variables to
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pass to make in the build step. These are passed before the +make+
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command. By default, empty.
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* +LIBFOO_MAKE_OPT+, to specify additional variables to pass to make
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in the build step. These are passed after the +make+ command. By
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default, empty.
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* +LIBFOO_INSTALL_STAGING_OPT+ contains the make options used to
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install the package to the staging directory. By default, the value
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is +DESTDIR=$$(STAGING_DIR) install+, which is correct for most
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CMake packages. It is still possible to override it.
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* +LIBFOO_INSTALL_TARGET_OPT+ contains the make options used to
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install the package to the target directory. By default, the value
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is +DESTDIR=$$(TARGET_DIR) install+. The default value is correct
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for most CMake packages, but it is still possible to override it if
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needed.
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* +LIBFOO_CLEAN_OPT+ contains the make options used to clean the
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package. By default, the value is +clean+.
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With the CMake infrastructure, all the steps required to build and
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install the packages are already defined, and they generally work well
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for most CMake-based packages. However, when required, it is still
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possible to customize what is done in any particular step:
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* By adding a post-operation hook (after extract, patch, configure,
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build or install). See the reference documentation of the generic
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infrastructure for details.
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* By overriding one of the steps. For example, even if the CMake
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infrastructure is used, if the package +.mk+ file defines its own
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+LIBFOO_CONFIGURE_CMDS+ variable, it will be used instead of the
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default CMake one. However, using this method should be restricted
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to very specific cases. Do not use it in the general case.
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