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SubjectRe: [PATCH] kbuild: work around distcc/icecc madness
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On Thu, 2009-03-19 at 22:02 +0100, Thomas Gleixner wrote:
> Impact: workaround for distcc/icecc
>
> Peter and I noticed that distcc and icecc based kernel compiles
> started to show random full kernel rebuilds even when nothing or just
> a .c file changed. The reason is "change of the command line" which
> caused scripts/mod/empty.o to rebuild and due to the dependencies the
> complete kernel tree. I never change the command line simply because I
> use a script for my builds.
>
> The root cause for this problem is the check for the CFI support in
> x86 binutils. The call is generated via:
>
> echo -e "$(1)" | $(CC) $(KBUILD_AFLAGS) -c -xassembler -o "$$TMP" -
>
> This works fine as long as a local gcc is used or distcc/icecc use the
> local machine. When distcc/icecc offload the compile to a remote
> machine the compile fails with the following error message:
> gcc: : No such file or directory
>
> Now we get command lines with -DCONFIG_CFI* and without every other
> compile which causes the full rebuilds.
>
> Digging trough the distcc/icecc code it seems that the stdin input for
> remote compiles is not handled correctly. Indeed there is some strange
> comment about this, but unfortunately no decision to compile it
> local. :(
>
> distcc and icecc are used by many developers and we can not fix the
> versions which are out there in the wild, but we can avoid the stdin
> based call easily: echo the asm code into the temp file which is used
> for the output and use it as input file for the compiler.

Yes, this makes it mostly work again... however,

On -linus I can do:

# cat distmake

#!/bin/bash

ARCH=$1; shift

export LD="nice -n19 ${ARCH}-linux-ld"
export AS="distcc ${ARCH}-linux-as"
export CC="distcc ${ARCH}-linux-gcc"

make LD="$LD" AS="$AS" CC="$CC" -j $DISTCC_SLOTS "$@"

# distmake x86_64 bzImage

to build the tree, and then use:

# make install

to install the resulting image. Note how the second make will use the
system gcc and not the distcc with cross arch toolchain.

This will still start a full rebuild on -tip. When I change my script to
use distmake x86_64 install, things work again after this patch.






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