Re: [Buildroot] [PATCH 3/3] toolchain/toolchain-wrapper: don't hardcode CCACHE_BASEDIR

From: Thomas Petazzoni via buildroot <buildroot@buildroot.org>
To: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Giulio Benetti <giulio.benetti@benettiengineering.com>,
	Romain Naour <romain.naour@gmail.com>,
	Thomas De Schampheleire <thomas.de_schampheleire@nokia.com>,
	Buildroot List <buildroot@buildroot.org>
Subject: Re: [Buildroot] [PATCH 3/3] toolchain/toolchain-wrapper: don't hardcode CCACHE_BASEDIR
Date: Sat, 6 Aug 2022 21:59:49 +0200	[thread overview]
Message-ID: <20220806215949.69ba40cf@windsurf> (raw)
In-Reply-To: <20220730121103.GR3168@scaer>

Howdy,

On Sat, 30 Jul 2022 14:11:03 +0200
"Yann E. MORIN" <yann.morin.1998@free.fr> wrote:

> And once this is fixed, you'll notice that the old and the new
> CCACHE_BASEDIR will be different:
> 
>     (before)$ BR2_DEBUG_WRAPPER=2 ./host/bin/arm-linux-gcc --help
>     ...
>     Toolchain wrapper executing:
>         CCACHE_BASEDIR='/home/ymorin/dev/buildroot/O/master'
>         '/home/ymorin/dev/buildroot/O/master/host/opt/ext-toolchain/bin/arm-linux-gcc.br_real'
>         ...
> 
>     (after)$ BR2_DEBUG_WRAPPER=2 ./host/bin/arm-linux-gcc --help
>     ...
>     Toolchain wrapper executing:
>         CCACHE_BASEDIR='/home/ymorin/dev/buildroot/O/master/host'
>         '/home/ymorin/dev/buildroot/O/master/host/opt/ext-toolchain/bin/arm-linux-gcc.br_real'
>         ...
> 
> So as you can see, before, CCACHE_BASEDIR was pointing to BASE_DIR, but
> now it points to HOST_DIR. This is one-level too deep, as it will not
> match the path where packages are actually built, which is
> BASE_DIR/build, and hapenned to be CCACHE_BASEDIR/build.
> 
> Even though I had the debug code path fixed, the second issue was not
> trivial enough for me to fix when applying, so I amrked the patch as
> changes requested.

You're totally right. And in fact, it makes the change useless. Indeed,
CCACHE_BASEDIR only makes sense when ccache is used during the
Buildroot build, because it points to $(BASE_DIR)... which once we are
outside of Buildroot, in the SDK, would no longer point to anything
sensible.

So instead, I've sent a different patch that sets the
CCACHE_COMPILERCHECK and CCACHE_BASEDIR environment variables, only if
ccache support is used (BR2_USE_CCACHE=1). Let me know what you think.

Thanks again for the good review!

Best regards,

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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