[OE-core] [RFC PATCH] Switch most global exports to task level

[Christopher Larson]

On Wed, May 25, 2016 at 9:49 AM, Christopher Larson <kergoth at gmail.com>
wrote:

> From: Christopher Larson <chris_larson at mentor.com>
>
> The majority of our global exports are only needed for the build tasks, so
> switch them to those tasks (configure/compile/install, but not
> populate_sysroot or package).
>
> Kept global exports: PATH, PSEUDO_DISABLED, LC_ALL, CCACHE_DIR,
> CCACHE_DISABLE
>
> The variables which are exported by default are listed in logically grouped
> variables, to make it easy to add or remove them from task exports:
>
> - PKG_CONFIG_EXPORTS: PKG_CONFIG_DIR, etc
> - BUILD_EXPORTS: BUILD_CC, etc
> - TARGET_EXPORTS: TARGET_CC, etc
> - TARGET_PATH_EXPORTS: prefix, bindir, etc
>
> Intermediate variables are added as well, to ease usage and avoid the need
> to
> mess with the flags directly for the common cases:
>
> - CONFIGURE_EXPORTS
> - COMPILE_EXPORTS
> - INSTALL_EXPORTS
> - POPULATE_SYSROOT_EXPORTS
> - PACKAGE_EXPORTS
>
> Future patches will pare down the exports from here. Specifically removing
> the
> default export of BUILD_EXPORTS, TARGET_EXPORTS, and TARGET_PATH_EXPORTS,
> none
> of which are consistently used by the buildsystems we're calling into.
>
> This is placed into conf/task-exports.conf, to avoid cluttering up
> bitbake.conf any further.
>
> Signed-off-by: Christopher Larson <chris_larson at mentor.com>
>

There are a couple exceptions for particular cases above and beyond this
patch, but not many, and I'm looking for thoughts on the approach and
direction here. Does this seem like a reasonable way to go?

Thinking about it, I should probably have mentioned the motivation behind
this in the commit message, I'll fix that. The issue is, global exports
(variables flagged as 'export') end up in the checksum of every single
task, as bitbake can't know where it's used and where it isn't, so I think
there's value in paring that down to make the checksums a bit less brittle.
-- 
Christopher Larson
kergoth at gmail dot com
Founder - BitBake, OpenEmbedded, OpenZaurus
Maintainer - Tslib
Senior Software Engineer, Mentor Graphics
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