[poky] Recompiles in Yocto/Poky

[Keskinarkaus, Teemu]

Hi,

I think there are some files that are being generated at compilation time so most likely those triggers the recompilation every time.

The next question is that how to I 'hide' files so that they don't trigger the recompilation? Is that something that I need to do on my application side or can I list files in Yocto to ignore when hashing files? This is most likely the proper way to deal with this issue rather than disabling whole feature.

Teemu Keskinarkaus
Software system engineer
maximatecc
making machines smart, safe and productive


-----Original Message-----
From: Paul Eggleton [mailto:paul.eggleton at linux.intel.com]
Sent: 8. kesäkuuta 2016 4:52
To: Peter Kjellerstedt; Keskinarkaus, Teemu
Cc: poky at yoctoproject.org
Subject: Re: [poky] Recompiles in Yocto/Poky

On Fri, 03 Jun 2016 07:00:14 Peter Kjellerstedt wrote:
> This is a feature introduced to complement the main use of
> externalsrc, which is together with devtool. When you use "devtool
> modify -x <recipe>", it fetches the sources as specified in the recipe
> and makes them available locally. At the same time it sets up a
> bbappend in the workspace layer which uses externalsrc to use those
> sources when building the recipe. This is intended to make it easy to
> use BitBake to actually work on and develop the sources. However, for
> this to work in practice, BitBake must rebuild the package if there
> are any changes in the sources, but since BitBake normally only looks
> at the meta data to determine if a recipe task needs to run, there is
> nothing telling it that the sources have changed. Therefore changes
> were made so that code specified using externalsrc is always rebuilt.

In 2.0 that's how it behaved - what it's supposed to do in 2.1 is determine if the sources have changed by either relying on the git metadata (if the source tree is tracked in git) or by hashing all files in the source tree if it isn't. It could be false triggering if you have files in the source tree that get regenerated as part of the compilation process that aren't hidden. Teemu, is that the case for your source tree?

Unfortunately there is no way at present to turn off this functionality; we could add one, however before doing that I would be more interested in looking at making the code more intelligent so it did automatically rebuild in response to source changes for this case and not when there were no changes, assuming that's practical.

Cheers,
Paul

--

Paul Eggleton
Intel Open Source Technology Centre

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