From: Arnout Vandecappelle via buildroot <buildroot@buildroot.org>
To: "Andreas Düring" <brpi@duering-andreas.de>, buildroot@buildroot.org
Subject: Re: [Buildroot] Buildroot does not use ccache for compiling Linux kernel?
Date: Sat, 14 Sep 2024 21:51:21 +0200 [thread overview]
Message-ID: <1456288c-ea8a-401d-bdec-c51d4fbdf09d@mind.be> (raw)
In-Reply-To: <20240914201937.567067fd@devuanPc.fritz.box>
On 14/09/2024 20:19, Andreas Düring via buildroot wrote:
> Hello,
>
> I am currently experimenting with building a minimal image for my
> Raspberry Pi.
>
> During this process, I realized that ccache, although enabled, is not
> used for compiling the Linux kernel.
That is very weird, because ccache is added by the toolchain wrapper. It can
only be disabled by setting BR2_USE_CCACHE=0 in the environment (or on the make
command line).
How did you determine that it doesn't use ccache?
> I think this is because of the
> recipe in linux/linux.mk:
>
> LINUX_MAKE_FLAGS = \
> HOSTCC="$(HOSTCC) $(subst -I/,-isystem /,$(subst -I /,-isystem /,$(HOST_CFLAGS))) $(HOST_LDFLAGS)" \
We explicitly don't use ccache here (HOSTCC doesn't use the wrapper, so it
needs to be added explicitly there). See commit 71a31b23 for an explanation why.
> ARCH=$(KERNEL_ARCH) \
> INSTALL_MOD_PATH=$(TARGET_DIR) \
> CROSS_COMPILE="$(TARGET_CROSS)" \
> WERROR=0 \
> REGENERATE_PARSERS=1 \
> DEPMOD=$(HOST_DIR)/sbin/depmod
>
>
> The linux kernel seems to assemble the compiler using TARGET_CROSS,
> e.g.
> CC = $(TARGET_CROSS)gcc
>
> As a very crude solution, I changed the corresponding line to
> CROSS_COMPILE="ccache $(TARGET_CROSS)"
This is what we had originally, but it was removed in commit 546a69db66ab
because it is now done by the wrapper.
Regards,
Arnout
> but this is probably not the optimal solution. (I didn't carefully
> check where else CROSS_COMPILE is used).
>
> If this is a known limitation? Should this be added to the
> documentation?
> https://buildroot.org/downloads/manual/manual.html#ccache
> ("This will automatically build ccache and use it for every host and
> target compilation.")
>
> With best regards,
> Andreas
> _______________________________________________
> buildroot mailing list
> buildroot@buildroot.org
> https://lists.buildroot.org/mailman/listinfo/buildroot
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prev parent reply other threads:[~2024-09-14 19:51 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-09-14 18:19 [Buildroot] Buildroot does not use ccache for compiling Linux kernel? Andreas Düring via buildroot
2024-09-14 18:25 ` Thomas Petazzoni via buildroot
2024-09-14 18:35 ` Andreas Düring via buildroot
2024-09-14 19:51 ` Arnout Vandecappelle via buildroot [this message]
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