[Buildroot] [RFCv3 06/15] package/pkg-generic: add the concept of extract dependency

[Yann E. MORIN <yann.morin.1998@free.fr>]

Thomas, All,

On 2017-12-01 21:53 +0100, Thomas Petazzoni spake thusly:
> Extract dependencies are dependencies that must be ready before the
> extract step of a package, i.e for tools that are needed to extract
> packages themselves. Current examples of such tools are host-tar,
> host-lzip and host-xz.
> 
> They are currently handled through DEPENDENCIES_HOST_PREREQ. However,
> this mechanism has a number of drawbacks:
> 
>  - First and foremost, because host-tar/host-lzip/host-xz are not
>    listed in the dependencies of packages, the package infrastructure
>    does not know it should rsync them in the context of per-package
>    SDK.
> 
>  - Second, there is no dependency handling *between* them. I.e, we
>    have no mechanism that says host-tar should be built before
>    host-lzip, while it is in fact the case: if you need to build
>    host-lzip, you need to extract a tarball, so you may need host-tar
>    if your system tarball is not capable enough.
> 
> For those reasons, it makes sense to add explicit support for "extract
> dependencies" in the package infrastructure, through the
> <pkg>_EXTRACT_DEPENDENCIES variable. It is unlikely this variable will
> ever be used by a package .mk file, but it will be used internally by
> the package infrastructure.
> 
> Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

Except for a typo (see below):

Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

> ---
> Changes since v2:
>  - New patch
> ---
>  docs/manual/adding-packages-generic.txt | 7 +++++++
>  package/pkg-generic.mk                  | 8 +++++++-
>  2 files changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/docs/manual/adding-packages-generic.txt b/docs/manual/adding-packages-generic.txt
> index 63ea51bf89..7f42cb09e9 100644
> --- a/docs/manual/adding-packages-generic.txt
> +++ b/docs/manual/adding-packages-generic.txt
> @@ -347,6 +347,13 @@ information is (assuming the package name is +libfoo+) :
>    a similar way, +HOST_LIBFOO_DEPENDENCIES+ lists the dependencies for
>    the current host package.
>  
> +* +LIBFOO_EXTRACT_DEPENDENCIES+ lists the dependencies (in terms of
> +  package name) that are required for the current target package to be
> +  extracted. These depnedencies are guaranteed to be compiled and
> +  installed before the extract step of the current package
> +  starts. This is only use internally by the package infrastructure,

*used

Regards,
Yann E. MORIN.

> +  and should typically not be used directly by packages.
> +
>  * +LIBFOO_PATCH_DEPENDENCIES+ lists the dependencies (in terms of
>    package name) that are required for the current package to be
>    patched. These dependencies are guaranteed to be extracted and
> diff --git a/package/pkg-generic.mk b/package/pkg-generic.mk
> index 2b821e9bdf..824c34bec9 100644
> --- a/package/pkg-generic.mk
> +++ b/package/pkg-generic.mk
> @@ -589,8 +589,13 @@ endif
>  
>  # Eliminate duplicates in dependencies
>  $(2)_FINAL_DEPENDENCIES = $$(sort $$($(2)_DEPENDENCIES))
> +$(2)_FINAL_EXTRACT_DEPENDENCIES = $$(sort $$($(2)_EXTRACT_DEPENDENCIES))
>  $(2)_FINAL_PATCH_DEPENDENCIES = $$(sort $$($(2)_PATCH_DEPENDENCIES))
> -$(2)_FINAL_ALL_DEPENDENCIES = $$(sort $$($(2)_FINAL_DEPENDENCIES) $$($(2)_FINAL_PATCH_DEPENDENCIES))
> +$(2)_FINAL_ALL_DEPENDENCIES = \
> +	$$(sort \
> +		$$($(2)_FINAL_DEPENDENCIES) \
> +		$$($(2)_FINAL_EXTRACT_DEPENDENCIES) \
> +		$$($(2)_FINAL_PATCH_DEPENDENCIES))
>  
>  $(2)_INSTALL_STAGING		?= NO
>  $(2)_INSTALL_IMAGES		?= NO
> @@ -716,6 +721,7 @@ $$($(2)_TARGET_PATCH):  | $$(patsubst %,%-patch,$$($(2)_FINAL_PATCH_DEPENDENCIES
>  
>  $(1)-extract:			$$($(2)_TARGET_EXTRACT)
>  $$($(2)_TARGET_EXTRACT):	$$($(2)_TARGET_SOURCE)
> +$$($(2)_TARGET_EXTRACT): | $$($(2)_FINAL_EXTRACT_DEPENDENCIES)
>  
>  $(1)-depends:		$$($(2)_FINAL_DEPENDENCIES)
>  
> -- 
> 2.13.6
> 

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