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From:   Masahiro Yamada <yamada.masahiro@socionext.com>
Date:   Thu, 8 Mar 2018 19:21:14 +0900
Message-ID: <CAK7LNARhhs4o-cKKzW9exRjbCYpTntdBvUgsx6o-egsTc2pQ0g@mail.gmail.com>
Subject: Re: [PATCH 2/5] kbuild: define KBUILD_MODNAME even if multiple
 modules share objects
To:     Cao jin <caoj.fnst@cn.fujitsu.com>
Cc:     Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        Sam Ravnborg <sam@ravnborg.org>,
        Michal Marek <michal.lkml@markovi.net>,
        Govind Singh <govinds@codeaurora.org>,
        Kalle Valo <kvalo@codeaurora.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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2018-03-08 19:11 GMT+09:00 Cao jin <caoj.fnst@cn.fujitsu.com>:
>
>
> On 03/08/2018 09:05 AM, Masahiro Yamada wrote:
>> Currently, KBUILD_MODNAME is defined only when $(modname) contains
>> just one word.  If an object is shared among multiple modules,
>> undefined KBUILD_MODNAME could cause a build error.  For example,
>> if CONFIG_DYNAMIC_DEBUG is enabled, any call of printk() populates
>> .modname, then fails to build due to undefined KBUILD_MODNAME.
>>
>> Take the following code as an example:
>>
>>   obj-m += foo.o
>>   obj-m += bar.o
>>   foo-objs := foo-bar-common.o foo-main.o
>>   bar-objs := foo-bar-common.o bar-main.o
>>
>> In this case, there is room for argument what to define for
>> KBUILD_MODNAME when foo-bar-common.o is being compiled.
>> "foo", "bar", or what else?
>>
>> One idea is to define colon-separated modules that share the object,
>> in this case, "bar:foo" (modules are sorted alphabetically by
>> $(sort ...).
>>
>> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
>> ---
>>
>>  scripts/Makefile.lib | 9 +++++----
>>  1 file changed, 5 insertions(+), 4 deletions(-)
>>
>> diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
>> index a7e315f..a1fbd6a 100644
>> --- a/scripts/Makefile.lib
>> +++ b/scripts/Makefile.lib
>> @@ -92,8 +92,7 @@ subdir-ym   := $(addprefix $(obj)/,$(subdir-ym))
>>  #       differ in different configs.
>>  name-fix = $(squote)$(quote)$(subst $(comma),_,$(subst -,_,$1))$(quote)$(squote)
>>  basename_flags = -DKBUILD_BASENAME=$(call name-fix,$(basetarget))
>> -modname_flags  = $(if $(filter 1,$(words $(modname))),\
>> -                 -DKBUILD_MODNAME=$(call name-fix,$(modname)))
>> +modname_flags  = -DKBUILD_MODNAME=$(call name-fix,$(modname))
>>
>
> I guess there is comment also need to be modified above this code hunk:
>
> Note: Files that end up in two or more modules are compiled without the
>       KBUILD_MODNAME definition. The reason is that any made-up name
>       would differ in different configs.


Why do I have to add lying comments here?

The commit subject/log claims KBUILD_MODNAME should be _always_ defined.


-- 
Best Regards
Masahiro Yamada