linux-kernel - Re: [RFC PATCH v1] checkpatch: Handle FILE pointer type

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Date:   Fri, 2 Sep 2022 13:04:04 +0200
From:   Mickaël Salaün <mic@...ikod.net>
To:     Joe Perches <joe@...ches.com>, Andy Whitcroft <apw@...onical.com>
Cc:     Dwaipayan Ray <dwaipayanray1@...il.com>,
        Lukas Bulwahn <lukas.bulwahn@...il.com>,
        Shuah Khan <shuah@...nel.org>, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org,
        Jerome Forissier <jerome.forissier@...aro.org>
Subject: Re: [RFC PATCH v1] checkpatch: Handle FILE pointer type


On 02/09/2022 12:39, Joe Perches wrote:
> On Fri, 2022-09-02 at 11:04 +0200, Mickaël Salaün wrote:
>> On 01/09/2022 20:22, Joe Perches wrote:
>>> On Thu, 2022-09-01 at 11:49 -0400, Joe Perches wrote:
>>>> On Thu, 2022-09-01 at 16:59 +0200, Mickaël Salaün wrote:
>>>>> When using a "FILE *" type, checkpatch considers this an error.  Fix
>>>>> this by explicitly defining "FILE" as a common type.
>>>> []
>>>>> Another error may be throw when we use FIXTURE_{DATA,VARIANT}() structs,
>>>>> as defined in kselftest_harness.h .
>>>> []
>>>>> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
>>>> []
>>>>> @@ -576,10 +576,17 @@ our $typeKernelTypedefs = qr{(?x:
>>>>>    	(?:__)?(?:u|s|be|le)(?:8|16|32|64)|
>>>>>    	atomic_t
>>>>>    )};
>>>>> +our $typeStdioTypedefs = qr{(?x:
>>>>> +	FILE
>>>>> +)};
>>>>
>>>> I'm fine with this.
>>>>
>>>>> +# our $typeKselftestHarnessTypedefs = qr{(?x:
>>>>> +# 	FIXTURE_(?:DATA|VARIANT)\($Ident\)
>>>>> +# )};
>>>>
>>>> But not this.  Random userspace typedefs should likely
>>>> be kept in some local version of checkpatch.
>>>>
>>>> Or maybe add a command line option like --additional_typedefs=<file>.
>>>
>>> Oops.  I forgot it already exists:
>>>
>>>     --typedefsfile             Read additional types from this file
>>>
>>> commit 75ad8c575a5ad105e2afc2051c68abceb9c65431
>>> Author: Jerome Forissier <jerome.forissier@...aro.org>
>>> Date:   Mon May 8 15:56:00 2017 -0700
>>>
>>>       checkpatch: add --typedefsfile
>>>       
>>>       When using checkpatch on out-of-tree code, it may occur that some
>>>       project-specific types are used, which will cause spurious warnings.
>>>       Add the --typedefsfile option as a way to extend the known types and
>>>       deal with this issue.
>>
>> This doesn't work for the FIXTURE_DATA() case.
> 
> checkpatch is a stupid little script.
> It's not a c preprocessor nor a syntax complete compiler.
> It's really easy for macros to make its output invalid.
> If you feed obfuscated c to checkpatch, it'd be confused.
> (Same is true for tools like coccinelle btw, though cocci is far better)
> checkpatch will never be comprehensive nor perfect.
> It's expected its users will use their common sense about its
> output message validity.
> 
>> And I'm not sure how
>> contributors would know that they need to use this option with a
>> specific file.
> 
> --help exists
> 
> Maybe Documentation/dev-tools/checkpatch.rst could be expanded for
> --verbose mode.

I was thinking about which file to use, but I understand your point. 
I'll send a v2 with only the "FILE" addition.
FIXTURE_{DATA,VARIANT}() will just not be handled but that's OK.