[OE-core] Quick question about OE-core/bitbake's re-building

[Tyler Hall]

On Sun, May 4, 2014 at 4:53 PM, Joel Fernandes <joelf at ti.com> wrote:

> How does it figure out when it needs to rebuild a package?
>

Bitbake generates hashes for every task that are based on the data that
will be used when running the task. This includes the body of the task
function, any variables it references, checksums of required files, and
hashes of tasks it depends on. This data is stored for each task in
$BUILDDIR/tmp/stamps. The task will re-run if a matching sigdata file does
not exist in the stamps directory. You can run bitbake-dumpsig on a sigdata
file to see what metadata changes will cause the task to rebuild.

For example if I modify the file:
>  ../meta/recipes-core/systemd/systemd-serialgetty/serial-getty at .service
>
> Does it track the modification time to know it needs to rebuild
> "systemd-serialgetty"?
>
> Because doing such a modification didn't cause it to rebuild.
>

The modification time won't trigger a rebuild since the contents hash the
same. Changing the contents of the file should trigger a rebuild, though.

-Tyler
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