Re: [PATCH 1/6] tools/build: Allow versioning of all LLVM tools defined in Makefile.include

[James Clark <james.clark@linaro.org>]

On 14/05/2026 11:02 am, bot+bpf-ci@kernel.org wrote:
>> tools/build: Allow versioning of all LLVM tools defined in Makefile.include
>>
>> The version of LLVM tools can be given on the build command with
>> LLVM=-15, but this isn't applied to all tools. For example $(CC) gets
>> versioned, but $(CLANG) doesn't. This causes a Perf build with LTO=1 to
>> fail with an error about mixed clang versions:
>>
>>   ld.lld: error: libperf/core.o: Unknown attribute kind (86)
>>     (Producer: 'LLVM18.1.8' Reader: 'LLVM 15.0.7')
>>
>> This file has two "ifneq ($(LLVM),)" blocks adjacent to each other, so
>> merge these blocks making it obvious that all tools should be versioned
>> consistently and there is nothing special about each block.
>>
>> This also reveals that ?= and "allow-override" are used inconsistently
>> between the blocks. "allow-override" is technically only required for
>> builtin variables, but isn't only used on them, and doesn't do any harm
>> if used on a non-builtin. Make them all "allow-override" for
>> consistency. The only functional difference this will cause is if there
>> is a file level definition of one of the variables followed by an
>> "#include of Makefile.include" which will now overwrite. But this isn't
>> done and in a later commit some of the duplicate definitions will be
>> removed for good measure.
>>
>> There are also some other LLVM tools that are not defined here and will
>> be moved in a later commit.
>>
>> Signed-off-by: James Clark <james.clark@linaro.org>
> 
> This looks like a bug fix that corrects inconsistent LLVM tool versioning
> introduced in an earlier commit. Should this include:
> 
>    Fixes: e9c281928c24 ("kbuild: Make $(LLVM) more flexible")
> 
> 
> ---
> AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
> See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
> 
> CI run summary: https://github.com/kernel-patches/bpf/actions/runs/25853166705

I did consider a fixes tag, but the only real bug is with Perf and 
LTO=1, and building it in this way has obviously never worked, so you 
could also argue this is new behavior.

I think it's quite and edge case and has some risk to break other tools 
if backported so I left the tag off.