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Re: [PATCH v1] misra: add deviation for rules 21.1 and 21.2


  • To: Dmytro Prokopchuk1 <dmytro_prokopchuk1@xxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Fri, 18 Jul 2025 07:31:50 +0200
  • Autocrypt: addr=jbeulich@xxxxxxxx; keydata= xsDiBFk3nEQRBADAEaSw6zC/EJkiwGPXbWtPxl2xCdSoeepS07jW8UgcHNurfHvUzogEq5xk hu507c3BarVjyWCJOylMNR98Yd8VqD9UfmX0Hb8/BrA+Hl6/DB/eqGptrf4BSRwcZQM32aZK 7Pj2XbGWIUrZrd70x1eAP9QE3P79Y2oLrsCgbZJfEwCgvz9JjGmQqQkRiTVzlZVCJYcyGGsD /0tbFCzD2h20ahe8rC1gbb3K3qk+LpBtvjBu1RY9drYk0NymiGbJWZgab6t1jM7sk2vuf0Py O9Hf9XBmK0uE9IgMaiCpc32XV9oASz6UJebwkX+zF2jG5I1BfnO9g7KlotcA/v5ClMjgo6Gl MDY4HxoSRu3i1cqqSDtVlt+AOVBJBACrZcnHAUSuCXBPy0jOlBhxPqRWv6ND4c9PH1xjQ3NP nxJuMBS8rnNg22uyfAgmBKNLpLgAGVRMZGaGoJObGf72s6TeIqKJo/LtggAS9qAUiuKVnygo 3wjfkS9A3DRO+SpU7JqWdsveeIQyeyEJ/8PTowmSQLakF+3fote9ybzd880fSmFuIEJldWxp Y2ggPGpiZXVsaWNoQHN1c2UuY29tPsJgBBMRAgAgBQJZN5xEAhsDBgsJCAcDAgQVAggDBBYC AwECHgECF4AACgkQoDSui/t3IH4J+wCfQ5jHdEjCRHj23O/5ttg9r9OIruwAn3103WUITZee e7Sbg12UgcQ5lv7SzsFNBFk3nEQQCACCuTjCjFOUdi5Nm244F+78kLghRcin/awv+IrTcIWF hUpSs1Y91iQQ7KItirz5uwCPlwejSJDQJLIS+QtJHaXDXeV6NI0Uef1hP20+y8qydDiVkv6l IreXjTb7DvksRgJNvCkWtYnlS3mYvQ9NzS9PhyALWbXnH6sIJd2O9lKS1Mrfq+y0IXCP10eS FFGg+Av3IQeFatkJAyju0PPthyTqxSI4lZYuJVPknzgaeuJv/2NccrPvmeDg6Coe7ZIeQ8Yj t0ARxu2xytAkkLCel1Lz1WLmwLstV30g80nkgZf/wr+/BXJW/oIvRlonUkxv+IbBM3dX2OV8 AmRv1ySWPTP7AAMFB/9PQK/VtlNUJvg8GXj9ootzrteGfVZVVT4XBJkfwBcpC/XcPzldjv+3 HYudvpdNK3lLujXeA5fLOH+Z/G9WBc5pFVSMocI71I8bT8lIAzreg0WvkWg5V2WZsUMlnDL9 mpwIGFhlbM3gfDMs7MPMu8YQRFVdUvtSpaAs8OFfGQ0ia3LGZcjA6Ik2+xcqscEJzNH+qh8V m5jjp28yZgaqTaRbg3M/+MTbMpicpZuqF4rnB0AQD12/3BNWDR6bmh+EkYSMcEIpQmBM51qM EKYTQGybRCjpnKHGOxG0rfFY1085mBDZCH5Kx0cl0HVJuQKC+dV2ZY5AqjcKwAxpE75MLFkr wkkEGBECAAkFAlk3nEQCGwwACgkQoDSui/t3IH7nnwCfcJWUDUFKdCsBH/E5d+0ZnMQi+G0A nAuWpQkjM1ASeQwSHEeAWPgskBQL
  • Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, "victorm.lira@xxxxxxx" <victorm.lira@xxxxxxx>, Federico Serafini <federico.serafini@xxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Julien Grall <julien@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
  • Delivery-date: Fri, 18 Jul 2025 05:32:01 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 17.07.2025 22:47, Dmytro Prokopchuk1 wrote:
> 
> 
> On 4/23/25 20:54, victorm.lira@xxxxxxx wrote:
>> From: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
>>
>> MISRA C Rules 21.1 ("#define and #undef shall not be used on a
>> reserved identifier or reserved macro name") and R21.2 ("A reserved
>> identifier or reserved macro name shall not be declared") violations
>> are not problematic for Xen, as it does not use the C or POSIX
>> libraries.
>>
>> Xen uses -fno-builtin and -nostdinc to ensure this, but there are still
>> __builtin_* functions from the compiler that are available so
>> a deviation is formulated for all identifiers not starting with
>> "__builtin_".
>>
>> The missing text of a deviation for Rule 21.2 is added to
>> docs/misra/deviations.rst.
>>
>> To avoid regressions, tag both rules as clean and add them to the
>> monitored set.
>>
>> Signed-off-by: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
>> Signed-off-by: Federico Serafini <federico.serafini@xxxxxxxxxxx>
>> Signed-off-by: Victor Lira <victorm.lira@xxxxxxx>
>> Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
>> ---
>> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>> Cc: Anthony PERARD <anthony.perard@xxxxxxxxxx>
>> Cc: Michal Orzel <michal.orzel@xxxxxxx>
>> Cc: Jan Beulich <jbeulich@xxxxxxxx>
>> Cc: Julien Grall <julien@xxxxxxx>
>> Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>
>> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
>> Cc: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
>> Cc: Federico Serafini <federico.serafini@xxxxxxxxxxx>
>> Cc: Bertrand Marquis <bertrand.marquis@xxxxxxx>
>> ---
>>   .../eclair_analysis/ECLAIR/deviations.ecl     |  9 ++++++-
>>   .../eclair_analysis/ECLAIR/monitored.ecl      |  2 ++
>>   automation/eclair_analysis/ECLAIR/tagging.ecl |  2 ++
>>   docs/misra/deviations.rst                     | 26 ++++++++++++++++++-
>>   4 files changed, 37 insertions(+), 2 deletions(-)
>>
>> diff --git a/automation/eclair_analysis/ECLAIR/deviations.ecl 
>> b/automation/eclair_analysis/ECLAIR/deviations.ecl
>> index 2c8fb92713..ffa23b53b7 100644
>> --- a/automation/eclair_analysis/ECLAIR/deviations.ecl
>> +++ b/automation/eclair_analysis/ECLAIR/deviations.ecl
>> @@ -639,8 +639,15 @@ in the expansion."
>>   # Series 21.
>>   #
>>
>> +-doc_begin="Xen does not use C and POSIX libraries:
>> +identifiers reserved by these libraries can be used safely, except for those
>> +beginning with '__builtin_'."
>> +-config=MC3A2.R21.1,macros={safe, "!^__builtin_.*$"}
>> +-config=MC3A2.R21.2,declarations={safe, "!^__builtin_.*$"}
>> +-doc_end
>> +
>>   -doc_begin="or, and and xor are reserved identifiers because they 
>> constitute alternate
>> -spellings for the corresponding operators (they are defined as macros by 
>> iso646.h).
>> +spellings for the corresponding logical operators (as defined in header 
>> 'iso646.h').
>>   However, Xen doesn't use standard library headers, so there is no risk of 
>> overlap."
>>   -config=MC3A2.R21.2,reports+={safe, 
>> "any_area(stmt(ref(kind(label)&&^(or|and|xor|not)$)))"}
>>   -doc_end
>> diff --git a/automation/eclair_analysis/ECLAIR/monitored.ecl 
>> b/automation/eclair_analysis/ECLAIR/monitored.ecl
>> index 8351996ec8..da229a0d84 100644
>> --- a/automation/eclair_analysis/ECLAIR/monitored.ecl
>> +++ b/automation/eclair_analysis/ECLAIR/monitored.ecl
>> @@ -79,6 +79,8 @@
>>   -enable=MC3A2.R20.12
>>   -enable=MC3A2.R20.13
>>   -enable=MC3A2.R20.14
>> +-enable=MC3A2.R21.1
>> +-enable=MC3A2.R21.2
>>   -enable=MC3A2.R21.3
>>   -enable=MC3A2.R21.4
>>   -enable=MC3A2.R21.5
>> diff --git a/automation/eclair_analysis/ECLAIR/tagging.ecl 
>> b/automation/eclair_analysis/ECLAIR/tagging.ecl
>> index 1d078d8905..3292bf751e 100644
>> --- a/automation/eclair_analysis/ECLAIR/tagging.ecl
>> +++ b/automation/eclair_analysis/ECLAIR/tagging.ecl
>> @@ -88,6 +88,8 @@ MC3A2.R20.11||
>>   MC3A2.R20.12||
>>   MC3A2.R20.13||
>>   MC3A2.R20.14||
>> +MC3A2.R21.1||
>> +MC3A2.R21.2||
>>   MC3A2.R21.3||
>>   MC3A2.R21.4||
>>   MC3A2.R21.5||
>> diff --git a/docs/misra/deviations.rst b/docs/misra/deviations.rst
>> index fe0b1e10a2..88328eaa8a 100644
>> --- a/docs/misra/deviations.rst
>> +++ b/docs/misra/deviations.rst
>> @@ -587,7 +587,31 @@ Deviations related to MISRA C:2012 Rules:
>>          construct is deviated only in Translation Units that present a 
>> violation
>>          of the Rule due to uses of this macro.
>>        - Tagged as `deliberate` for ECLAIR.
>> -
>> +
>> +   * - R21.1
>> +     - Rule 21.1 reports identifiers reserved for the C and POSIX standard
>> +       libraries. Xen does not use such libraries and all translation units
>> +       are compiled with option '-nostdinc', therefore there is no reason to
>> +       avoid to use `#define` or `#undef` on such identifiers except for 
>> those
>> +       beginning with `__builtin_` for which compilers may perform (wrong)
>> +       optimizations.
>> +     - Tagged as `safe` for ECLAIR.
>> +
>> +   * - R21.2
>> +     - Rule 21.2 reports identifiers reserved for the C and POSIX standard
>> +       libraries. Xen does not use such libraries and all translation units
>> +       are compiled with option '-nostdinc', therefore there is no reason to
>> +       avoid declaring such identifiers except for those beginning with
>> +       `__builtin_` for which compilers may perform (wrong) optimizations.
>> +     - Tagged as `safe` for ECLAIR.
>> +
>> +   * - R21.2
>> +     - `or`, `and` and `xor` are reserved identifiers because they 
>> constitute
>> +       alternate spellings for the corresponding logical operators
>> +       (as defined in Standard Library header `\<iso646.h\>`). Xen does not 
>> use
>> +       Standard library headers, so there is no risk of overlap.
>> +     - Tagged as `safe` for ECLAIR.
>> +
>>      * - R21.9
>>        - Xen does not use the `bsearch` and `qsort` functions provided by 
>> the C
>>          Standard Library, but provides in source form its own 
>> implementation,
>> --
>> 2.47.0
> 
> Hello All!
> 
> I tried to play with Rule 21.1 deviations.
> 
> After applying the following configurations:
> 
> -config=MC3A2.R21.1,macros+={safe, "^offsetof$ || ^(is|to)[a-z]+$ || 
> name(NULL) || name(bool) || name(true) || name(false)"}
> -config=MC3A2.R21.1,macros+={safe, 
> "loc(file(^xen/include/xen/inttypes\\.h$))"}
> -config=MC3A2.R21.1,macros+={safe, "loc(file(^xen/include/xen/types\\.h$))"}
> -config=MC3A2.R21.1,macros+={safe, "^str[a-z]+$ || ^(v)?sprintf$ || 
> ^va_[a-z]+$"}

Can you spell these out in words? I can only vaguely interpret these Eclair
patterns, sorry.

> Eclair showed 699 remaining violations.
> All of them were related to names beginning with an underscore (_).
> 
> It's possible to resolve the rest of them with help of (all, except for 
> those beginning with '__builtin_' and '__x86_64__'):
> 
> -config=MC3A2.R21.1,macros+={safe, "^_.*$ && !^__builtin_.*$ && 
> !^__x86_64__$"}
> 
> Probably, the exception list can be extended.
> 
> Jan,
> I know you don't want to disallow "_all_" such reserved identifiers.
> But how to deal with that?

How do I not want this? I've been arguing for years that we should respect
the reserved name spaces. (Did you perhaps mean "... you don't want to
deviate ..."?) There are exceptions, yes, e.g. ...

> Try to cover all macros? Like this, for example (I assume that there are 
> no such reserved macros):
> -config=MC3A2.R21.1,macros+={safe, "^.*XEN.*$ || ^.*HYPERVISOR.*$"}

... anything we may have (wrongly) introduced into the public headers. We
can't very well change naming there.

Jan



 


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