buildroot/docs/manual/adding-packages-hooks.txt

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[[hooks]]
=== Hooks available in the various build steps

The generic infrastructure (and as a result also the derived autotools
and cmake infrastructures) allow packages to specify hooks.
These define further actions to perform after existing steps.
Most hooks aren't really useful for generic packages, since the +.mk+
file already has full control over the actions performed in each step
of the package construction.

The following hook points are available:

* +LIBFOO_POST_DOWNLOAD_HOOKS+
* +LIBFOO_POST_EXTRACT_HOOKS+
* +LIBFOO_POST_RSYNC_HOOKS+
* +LIBFOO_PRE_PATCH_HOOKS+
* +LIBFOO_POST_PATCH_HOOKS+
* +LIBFOO_PRE_CONFIGURE_HOOKS+
* +LIBFOO_POST_CONFIGURE_HOOKS+
* +LIBFOO_POST_BUILD_HOOKS+
* +LIBFOO_POST_INSTALL_HOOKS+ (for host packages only)
* +LIBFOO_POST_INSTALL_STAGING_HOOKS+ (for target packages only)
* +LIBFOO_POST_INSTALL_TARGET_HOOKS+ (for target packages only)
* +LIBFOO_POST_LEGAL_INFO_HOOKS+

These variables are 'lists' of variable names containing actions to be
performed at this hook point. This allows several hooks to be
registered at a given hook point. Here is an example:

----------------------
define LIBFOO_POST_PATCH_FIXUP
	action1
	action2
endef

LIBFOO_POST_PATCH_HOOKS += LIBFOO_POST_PATCH_FIXUP
----------------------

==== Using the +POST_RSYNC+ hook
The +POST_RSYNC+ hook is run only for packages that use a local source,
either through the +local+ site method or the +OVERRIDE_SRCDIR+
mechanism. In this case, package sources are copied using +rsync+ from
the local location into the buildroot build directory. The +rsync+
command does not copy all files from the source directory, though.
Files belonging to a version control system, like the directories
+.git+, +.hg+, etc. are not copied. For most packages this is
sufficient, but a given package can perform additional actions using
the +POST_RSYNC+ hook.

In principle, the hook can contain any command you want. One specific
use case, though, is the intentional copying of the version control
directory using +rsync+. The +rsync+ command you use in the hook can, among
others, use the following variables:

* +$(SRCDIR)+: the path to the overridden source directory
* +$(@D)+: the path to the build directory