[Xen-devel] Re: [PATCH] Detect distro-variant directories at build-time

[Bruce Edge <bruce.edge@xxxxxxxxx>]

On Tue, Sep 21, 2010 at 4:19 AM, Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx> wrote:
> Sadly I didn't double-check all the ramifications of Bruce's patch in
> quite enough detail and missed a side-effect.  I think it would be
> better to auto-detect everything at build-time as well as at run-time,
> and this should make all of this stuff much less of a source of
> tripping-over.
>
> Ian.

Definitely a better option. Thanks for fixing it.

-Bruce

>
> # HG changeset patch
> # User Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
> # Date 1285067824 -3600
> # Node ID c41252a55a0a0da08bfca98e65a7075f1af27ed0
> # Parent  7167d6dd5c7c6597ca8e2ce416295b44fb1bcf65
> tools, build system: Detect distro-variant directories at build-time
>
> In b59f87f56b1e, the defaults for some of the directory config
> variables implicitly changed.  In this commit we arrange for the
> defaults to be auto-detected (with the same logic as the run-time
> scripts use).
>
> This will make the build more likely to produce answers which the
> builder intends.  (And, in particular, it should un-break the
> automated tests, which didn't set these variables explicitly and
> therefore got broken by b59f87f56b1e.)
>
> Signed-off-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
>
> diff -r 7167d6dd5c7c -r c41252a55a0a Config.mk
> --- a/Config.mk Mon Sep 20 20:11:43 2010 +0100
> +++ b/Config.mk Tue Sep 21 12:17:04 2010 +0100
> @@ -31,11 +31,21 @@ MANDIR      ?= $(SHAREDIR)/man
>  MANDIR      ?= $(SHAREDIR)/man
>  BASH_COMPLETION_DIR ?= $(CONFIG_DIR)/bash_completion.d
>
> -# These are the Red Hat settings.
> +# arguments: variable, common path part, path to test, if yes, if no
> +define setvar_dir
> +  ifndef $(1)
> +    ifneq (,$(wildcard $(2)$(3)))
> +      $(1) ?= $(2)$(4)
> +    else
> +      $(1) ?= $(2)$(5)
> +    endif
> +  endif
> +endef
> +
>  # See distro_mapping.txt for other options
> -CONFIG_LEAF_DIR ?= sysconfig
> -SUBSYS_DIR ?= /var/run/subsys
> -INITD_DIR ?= /etc/rc.d/init.d
> +$(eval $(call setvar_dir,CONFIG_LEAF_DIR,,/etc/sysconfig,sysconfig,default))
> +$(eval $(call setvar_dir,SUBSYS_DIR,/var/run,/subsys,/subsys,))
> +$(eval $(call setvar_dir,INITD_DIR,/etc,/rc.d/init.d,/rc.d/init.d,/init.d))
>
>  ifneq ($(EXTRA_PREFIX),)
>  EXTRA_INCLUDES += $(EXTRA_PREFIX)/include
> diff -r 7167d6dd5c7c -r c41252a55a0a docs/misc/distro_mapping.txt
> --- a/docs/misc/distro_mapping.txt      Mon Sep 20 20:11:43 2010 +0100
> +++ b/docs/misc/distro_mapping.txt      Tue Sep 21 12:17:04 2010 +0100
> @@ -2,26 +2,26 @@ other distros one needs to set the varia
>  other distros one needs to set the variables for the elements below
>
>  -----------------+------------------+---------------+----------------+
> -                 | RedHat (default) |  Debian       |  Suse          |
> +                 | Red Hat          |  Debian       |  Suse          |
>  -----------------+------------------+---------------+----------------+
>  CONFIG_LEAF_DIR  | sysconfig        | default       | sysconfig      |
>  SUBSYS_DIR       | /var/run/subsys  | /var/run      | /var/run       |
>  INITD_DIR        | /etc/rc.d/init.d | /etc/init.d   | /etc/init.d    |
>  -----------------+------------------+---------------+----------------+
>
> -The build currently defaults to the elements used by Red Hat.
> -For others, these env variables must be set in the shell env
> -or modified in Config.mk before running make.
> +The existence of these directories are tested at build-time (on the
> +build host, via the "setvar_dir" macro in Config.mk) and for some
> +scripts at run-time.  If the Red Hat directory exists, it is used;
> +otherwise the Debian one is used.
>
> -This mechanism sets the location that files are installed to, but does
> -not change the code itself. Scripts that refer to files affected by these
> -directories must check each possible location at run time.
> +You can override this by setting the variables in the environment or
> +your ".config" (which is included by .config).
>
>  To add support for new distributions that don't use the above locations,
>  one must grep for the above elements and add appropriate checks.
>
> -For example if a new distro uses /etc/bork as it's config dir, It's not
> -sufficient to set CONFIG_LEAF_DIR=bork, one must also add tests for the
> +For example if a new distro uses /etc/bork as its config dir, it's not
> +sufficient to set CONFIG_LEAF_DIR=bork; one must also add tests for the
>  existance of the bork dir in every context where config files are read.
>
>
>

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