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Date:   Thu, 14 Jan 2021 13:32:45 -0800
From:   jjohnson@codeaurora.org
To:     Nick Desaulniers <ndesaulniers@google.com>
Cc:     eberman@quicinc.com, linux-kbuild@vger.kernel.org,
        linux-kernel@vger.kernel.org, masahiroy@kernel.org,
        michal.lkml@markovi.net, mkalikot@codeaurora.org,
        psodagud@quicinc.com,
        ndesaulniers via sendgmr 
        <ndesaulniers@ndesaulniers1.mtv.corp.google.com>
Subject: Re: [PATCH 2/2] kbuild: handle excessively long argument lists
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On 2021-01-14 13:07, Nick Desaulniers wrote:
>> From: Mahesh Kumar Kalikot Veetil <mkalikot@codeaurora.org>
>> 
>> Modules with a large number of compilation units may be
>> exceeding AR and LD command argument list. Handle this gracefully by
>> writing the long argument list in a file. The command line options
>> read from file are inserted in place of the original @file option.
>> 
>> The usage is well documented at
>> https://www.gnu.org/software/make/manual/html_node/File-Function.html
>> 
>> Signed-off-by: Mahesh Kumar Kalikot Veetil <mkalikot@codeaurora.org>
>> Signed-off-by: Jeff Johnson <jjohnson@codeaurora.org>
>> ---
>>  scripts/Makefile.build | 6 +++++-
>>  1 file changed, 5 insertions(+), 1 deletion(-)
>> 
>> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
>> index 252b7d2..d5ef345 100644
>> --- a/scripts/Makefile.build
>> +++ b/scripts/Makefile.build
>> @@ -425,7 +425,11 @@ $(obj)/lib.a: $(lib-y) FORCE
>>  # module is turned into a multi object module, $^ will contain header 
>> file
>>  # dependencies recorded in the .*.cmd file.
>>  quiet_cmd_link_multi-m = LD [M]  $@
>> -      cmd_link_multi-m = $(LD) $(ld_flags) -r -o $@ $(filter %.o,$^)
>> +      cmd_link_multi-m =					\
>> +	$(file >$@.in,$(filter %.o,$^))				\
>> +	$(LD) $(ld_flags) -r -o $@ @$@.in;			\
>> +	rm -f $@.in
>> +endif
> 
> Was this build tested?
> 
> $ make LLVM=1 LLVM_IAS=1 -j72 defconfig
> scripts/Makefile.build:432: *** extraneous 'endif'.  Stop.
> make: *** [Makefile:535: scripts_basic] Error 2
> 
> (Please cc me on v2)

blush

It was tested on a workspace that also contains the Clang LTO series
https://patchwork.kernel.org/project/linux-kbuild/patch/20201211184633.3213045-3-samitolvanen@google.com/

I messed up when trimming, will update in v2