| Message ID | alpine.DEB.2.22.394.2407301626460.4857@ubuntu-linux-20-04-desktop (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | docs/misra: add R13.2 and R18.2 to rules.rst | expand |
On 31.07.2024 01:30, Stefano Stabellini wrote: > --- a/docs/misra/rules.rst > +++ b/docs/misra/rules.rst > @@ -462,6 +462,15 @@ maintainers if you want to suggest a change. > - Initializer lists shall not contain persistent side effects > - > > + * - `Rule 13.2 <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_13_02.c>`_ > + - Required > + - The value of an expression and its persistent side-effects shall > + be the same under all permitted evaluation orders > + - Be aware that the static analysis tool Eclair might report > + several findings for Rule 13.2 of type "caution". These are > + instances where Eclair is unable to verify that the code is valid > + in regard to Rule 13.2. Caution reports are not violations. Which doesn't make clear what our take is towards new code people may submit. > @@ -583,6 +592,15 @@ maintainers if you want to suggest a change. > submitting new patches please try to decrease the number of > violations when possible. > > + * - `Rule 18.2 <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_18_02.c>`_ > + - Required > + - Subtraction between pointers shall only be applied to pointers > + that address elements of the same array > + - Be aware that the static analysis tool Eclair might report > + several findings for Rule 18.2 of type "caution". These are > + instances where Eclair is unable to verify that the code is valid > + in regard to Rule 18.2. Caution reports are not violations. And while the same wording is used here, I think it is pretty clear for this that we'd reject changes where bad subtractions are used. IOW even more so important to clarify the (possibly different) positions on what is going to be added into the code base. Jan
On Wed, 31 Jul 2024, Jan Beulich wrote: > On 31.07.2024 01:30, Stefano Stabellini wrote: > > --- a/docs/misra/rules.rst > > +++ b/docs/misra/rules.rst > > @@ -462,6 +462,15 @@ maintainers if you want to suggest a change. > > - Initializer lists shall not contain persistent side effects > > - > > > > + * - `Rule 13.2 <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_13_02.c>`_ > > + - Required > > + - The value of an expression and its persistent side-effects shall > > + be the same under all permitted evaluation orders > > + - Be aware that the static analysis tool Eclair might report > > + several findings for Rule 13.2 of type "caution". These are > > + instances where Eclair is unable to verify that the code is valid > > + in regard to Rule 13.2. Caution reports are not violations. > > Which doesn't make clear what our take is towards new code people may > submit. Good point, see my comment below > > @@ -583,6 +592,15 @@ maintainers if you want to suggest a change. > > submitting new patches please try to decrease the number of > > violations when possible. > > > > + * - `Rule 18.2 <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_18_02.c>`_ > > + - Required > > + - Subtraction between pointers shall only be applied to pointers > > + that address elements of the same array > > + - Be aware that the static analysis tool Eclair might report > > + several findings for Rule 18.2 of type "caution". These are > > + instances where Eclair is unable to verify that the code is valid > > + in regard to Rule 18.2. Caution reports are not violations. > > And while the same wording is used here, I think it is pretty clear for > this that we'd reject changes where bad subtractions are used. IOW even > more so important to clarify the (possibly different) positions on what > is going to be added into the code base. In both of these cases, we would reject code that doesn't follow R13.2 and R18.2. I'll change it to the following: Be aware that the static analysis tool Eclair might report several findings for Rule 18.2 of type "caution". These are instances where Eclair is unable to verify that the code is valid in regard to Rule 18.2. Caution reports are not violations. Regardless, new code is expected to follow this rule.
Hi Stefano, > On 1 Aug 2024, at 01:50, Stefano Stabellini <sstabellini@kernel.org> wrote: > > On Wed, 31 Jul 2024, Jan Beulich wrote: >> On 31.07.2024 01:30, Stefano Stabellini wrote: >>> --- a/docs/misra/rules.rst >>> +++ b/docs/misra/rules.rst >>> @@ -462,6 +462,15 @@ maintainers if you want to suggest a change. >>> - Initializer lists shall not contain persistent side effects >>> - >>> >>> + * - `Rule 13.2 <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_13_02.c>`_ >>> + - Required >>> + - The value of an expression and its persistent side-effects shall >>> + be the same under all permitted evaluation orders >>> + - Be aware that the static analysis tool Eclair might report >>> + several findings for Rule 13.2 of type "caution". These are >>> + instances where Eclair is unable to verify that the code is valid >>> + in regard to Rule 13.2. Caution reports are not violations. >> >> Which doesn't make clear what our take is towards new code people may >> submit. > > Good point, see my comment below > > >>> @@ -583,6 +592,15 @@ maintainers if you want to suggest a change. >>> submitting new patches please try to decrease the number of >>> violations when possible. >>> >>> + * - `Rule 18.2 <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_18_02.c>`_ >>> + - Required >>> + - Subtraction between pointers shall only be applied to pointers >>> + that address elements of the same array >>> + - Be aware that the static analysis tool Eclair might report >>> + several findings for Rule 18.2 of type "caution". These are >>> + instances where Eclair is unable to verify that the code is valid >>> + in regard to Rule 18.2. Caution reports are not violations. >> >> And while the same wording is used here, I think it is pretty clear for >> this that we'd reject changes where bad subtractions are used. IOW even >> more so important to clarify the (possibly different) positions on what >> is going to be added into the code base. > > In both of these cases, we would reject code that doesn't follow R13.2 > and R18.2. I'll change it to the following: > > > Be aware that the static analysis tool Eclair might report several > findings for Rule 18.2 of type "caution". These are instances where > Eclair is unable to verify that the code is valid in regard to Rule > 18.2. Caution reports are not violations. Regardless, new code is > expected to follow this rule. I think that in both cases it is wrong to state that "cautions reported are not violations" where those are cases where the tool is not sure so they might be or not violations. So I would change the sentence to "cautions might not be violations. The rule should be followed in any case in new code submitted". Cheers Bertrand
On 01.08.2024 01:50, Stefano Stabellini wrote: > On Wed, 31 Jul 2024, Jan Beulich wrote: >> On 31.07.2024 01:30, Stefano Stabellini wrote: >>> --- a/docs/misra/rules.rst >>> +++ b/docs/misra/rules.rst >>> @@ -462,6 +462,15 @@ maintainers if you want to suggest a change. >>> - Initializer lists shall not contain persistent side effects >>> - >>> >>> + * - `Rule 13.2 <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_13_02.c>`_ >>> + - Required >>> + - The value of an expression and its persistent side-effects shall >>> + be the same under all permitted evaluation orders >>> + - Be aware that the static analysis tool Eclair might report >>> + several findings for Rule 13.2 of type "caution". These are >>> + instances where Eclair is unable to verify that the code is valid >>> + in regard to Rule 13.2. Caution reports are not violations. >> >> Which doesn't make clear what our take is towards new code people may >> submit. > > Good point, see my comment below > > >>> @@ -583,6 +592,15 @@ maintainers if you want to suggest a change. >>> submitting new patches please try to decrease the number of >>> violations when possible. >>> >>> + * - `Rule 18.2 <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_18_02.c>`_ >>> + - Required >>> + - Subtraction between pointers shall only be applied to pointers >>> + that address elements of the same array >>> + - Be aware that the static analysis tool Eclair might report >>> + several findings for Rule 18.2 of type "caution". These are >>> + instances where Eclair is unable to verify that the code is valid >>> + in regard to Rule 18.2. Caution reports are not violations. >> >> And while the same wording is used here, I think it is pretty clear for >> this that we'd reject changes where bad subtractions are used. IOW even >> more so important to clarify the (possibly different) positions on what >> is going to be added into the code base. > > In both of these cases, we would reject code that doesn't follow R13.2 > and R18.2. But we shouldn't (unconditionally) do so for for 13.2, should we? > I'll change it to the following: > > > Be aware that the static analysis tool Eclair might report several > findings for Rule 18.2 of type "caution". These are instances where > Eclair is unable to verify that the code is valid in regard to Rule > 18.2. Caution reports are not violations. Regardless, new code is > expected to follow this rule. I'm fine with this for 18.2, but not so much for 13.2. Jan
On Thu, 1 Aug 2024, Jan Beulich wrote: > On 01.08.2024 01:50, Stefano Stabellini wrote: > > On Wed, 31 Jul 2024, Jan Beulich wrote: > >> On 31.07.2024 01:30, Stefano Stabellini wrote: > >>> --- a/docs/misra/rules.rst > >>> +++ b/docs/misra/rules.rst > >>> @@ -462,6 +462,15 @@ maintainers if you want to suggest a change. > >>> - Initializer lists shall not contain persistent side effects > >>> - > >>> > >>> + * - `Rule 13.2 <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_13_02.c>`_ > >>> + - Required > >>> + - The value of an expression and its persistent side-effects shall > >>> + be the same under all permitted evaluation orders > >>> + - Be aware that the static analysis tool Eclair might report > >>> + several findings for Rule 13.2 of type "caution". These are > >>> + instances where Eclair is unable to verify that the code is valid > >>> + in regard to Rule 13.2. Caution reports are not violations. > >> > >> Which doesn't make clear what our take is towards new code people may > >> submit. > > > > Good point, see my comment below > > > > > >>> @@ -583,6 +592,15 @@ maintainers if you want to suggest a change. > >>> submitting new patches please try to decrease the number of > >>> violations when possible. > >>> > >>> + * - `Rule 18.2 <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_18_02.c>`_ > >>> + - Required > >>> + - Subtraction between pointers shall only be applied to pointers > >>> + that address elements of the same array > >>> + - Be aware that the static analysis tool Eclair might report > >>> + several findings for Rule 18.2 of type "caution". These are > >>> + instances where Eclair is unable to verify that the code is valid > >>> + in regard to Rule 18.2. Caution reports are not violations. > >> > >> And while the same wording is used here, I think it is pretty clear for > >> this that we'd reject changes where bad subtractions are used. IOW even > >> more so important to clarify the (possibly different) positions on what > >> is going to be added into the code base. > > > > In both of these cases, we would reject code that doesn't follow R13.2 > > and R18.2. > > But we shouldn't (unconditionally) do so for for 13.2, should we? > > > I'll change it to the following: > > > > > > Be aware that the static analysis tool Eclair might report several > > findings for Rule 18.2 of type "caution". These are instances where > > Eclair is unable to verify that the code is valid in regard to Rule > > 18.2. Caution reports are not violations. Regardless, new code is > > expected to follow this rule. > > I'm fine with this for 18.2, but not so much for 13.2. Let me clarify something about R13.2. I expect we are aligned on this. Rule 13.2 only expects that "the value of an expression and its persistent side-effects shall be the same under all permitted evaluation orders" and nothing more. It is an outstanding limitation of static analyzers such as ECLAIR that they cannot be certain that "the value of an expression and its persistent side-effects shall be the same under all permitted evaluation orders". So one way to make ECLAIR happy is to change this code: 1) func1(param1, func2(a), func3(b); into this code: 2) param2 = func2(a); param3 = func3(b); func1(param1, param2, param3); Rule 13.2 is not asking us to change 1) into 2). 1) is acceptable. It is just that ECLAIR cannot help us ensure that 1) is compliant with Rule 13.2. It is totally fine to accept new code written in the form 1), of course only if "the value of an expression and its persistent side-effects shall be the same under all permitted evaluation orders". It would likely increase the number of ECLAIR cautions, but it is not necessarily a problem, and the ECLAIR Gitlab job will not fail. If one of the reviewers discovers that 1) doesn't comply with Rule 13.2 due to manual review, then they should ask the contributor to change the code. That is a good idea because we wouldn't want the value of an expression to be dependant on the evaluation order which GCC cannot guarantee.
On Thu, 1 Aug 2024, Bertrand Marquis wrote: > Hi Stefano, > > > On 1 Aug 2024, at 01:50, Stefano Stabellini <sstabellini@kernel.org> wrote: > > > > On Wed, 31 Jul 2024, Jan Beulich wrote: > >> On 31.07.2024 01:30, Stefano Stabellini wrote: > >>> --- a/docs/misra/rules.rst > >>> +++ b/docs/misra/rules.rst > >>> @@ -462,6 +462,15 @@ maintainers if you want to suggest a change. > >>> - Initializer lists shall not contain persistent side effects > >>> - > >>> > >>> + * - `Rule 13.2 <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_13_02.c>`_ > >>> + - Required > >>> + - The value of an expression and its persistent side-effects shall > >>> + be the same under all permitted evaluation orders > >>> + - Be aware that the static analysis tool Eclair might report > >>> + several findings for Rule 13.2 of type "caution". These are > >>> + instances where Eclair is unable to verify that the code is valid > >>> + in regard to Rule 13.2. Caution reports are not violations. > >> > >> Which doesn't make clear what our take is towards new code people may > >> submit. > > > > Good point, see my comment below > > > > > >>> @@ -583,6 +592,15 @@ maintainers if you want to suggest a change. > >>> submitting new patches please try to decrease the number of > >>> violations when possible. > >>> > >>> + * - `Rule 18.2 <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_18_02.c>`_ > >>> + - Required > >>> + - Subtraction between pointers shall only be applied to pointers > >>> + that address elements of the same array > >>> + - Be aware that the static analysis tool Eclair might report > >>> + several findings for Rule 18.2 of type "caution". These are > >>> + instances where Eclair is unable to verify that the code is valid > >>> + in regard to Rule 18.2. Caution reports are not violations. > >> > >> And while the same wording is used here, I think it is pretty clear for > >> this that we'd reject changes where bad subtractions are used. IOW even > >> more so important to clarify the (possibly different) positions on what > >> is going to be added into the code base. > > > > In both of these cases, we would reject code that doesn't follow R13.2 > > and R18.2. I'll change it to the following: > > > > > > Be aware that the static analysis tool Eclair might report several > > findings for Rule 18.2 of type "caution". These are instances where > > Eclair is unable to verify that the code is valid in regard to Rule > > 18.2. Caution reports are not violations. Regardless, new code is > > expected to follow this rule. > > I think that in both cases it is wrong to state that "cautions reported are > not violations" where those are cases where the tool is not sure so they > might be or not violations. > So I would change the sentence to "cautions might not be violations. The > rule should be followed in any case in new code submitted". I am happy with your wording, I'll make the change
On 01.08.2024 19:59, Stefano Stabellini wrote: > On Thu, 1 Aug 2024, Jan Beulich wrote: >> On 01.08.2024 01:50, Stefano Stabellini wrote: >>> On Wed, 31 Jul 2024, Jan Beulich wrote: >>>> On 31.07.2024 01:30, Stefano Stabellini wrote: >>>>> --- a/docs/misra/rules.rst >>>>> +++ b/docs/misra/rules.rst >>>>> @@ -462,6 +462,15 @@ maintainers if you want to suggest a change. >>>>> - Initializer lists shall not contain persistent side effects >>>>> - >>>>> >>>>> + * - `Rule 13.2 <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_13_02.c>`_ >>>>> + - Required >>>>> + - The value of an expression and its persistent side-effects shall >>>>> + be the same under all permitted evaluation orders >>>>> + - Be aware that the static analysis tool Eclair might report >>>>> + several findings for Rule 13.2 of type "caution". These are >>>>> + instances where Eclair is unable to verify that the code is valid >>>>> + in regard to Rule 13.2. Caution reports are not violations. >>>> >>>> Which doesn't make clear what our take is towards new code people may >>>> submit. >>> >>> Good point, see my comment below >>> >>> >>>>> @@ -583,6 +592,15 @@ maintainers if you want to suggest a change. >>>>> submitting new patches please try to decrease the number of >>>>> violations when possible. >>>>> >>>>> + * - `Rule 18.2 <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_18_02.c>`_ >>>>> + - Required >>>>> + - Subtraction between pointers shall only be applied to pointers >>>>> + that address elements of the same array >>>>> + - Be aware that the static analysis tool Eclair might report >>>>> + several findings for Rule 18.2 of type "caution". These are >>>>> + instances where Eclair is unable to verify that the code is valid >>>>> + in regard to Rule 18.2. Caution reports are not violations. >>>> >>>> And while the same wording is used here, I think it is pretty clear for >>>> this that we'd reject changes where bad subtractions are used. IOW even >>>> more so important to clarify the (possibly different) positions on what >>>> is going to be added into the code base. >>> >>> In both of these cases, we would reject code that doesn't follow R13.2 >>> and R18.2. >> >> But we shouldn't (unconditionally) do so for for 13.2, should we? >> >>> I'll change it to the following: >>> >>> >>> Be aware that the static analysis tool Eclair might report several >>> findings for Rule 18.2 of type "caution". These are instances where >>> Eclair is unable to verify that the code is valid in regard to Rule >>> 18.2. Caution reports are not violations. Regardless, new code is >>> expected to follow this rule. >> >> I'm fine with this for 18.2, but not so much for 13.2. > > Let me clarify something about R13.2. I expect we are aligned on this. > > Rule 13.2 only expects that "the value of an expression and its persistent > side-effects shall be the same under all permitted evaluation orders" > and nothing more. > > It is an outstanding limitation of static analyzers such as ECLAIR > that they cannot be certain that "the value of an expression and its > persistent side-effects shall be the same under all permitted evaluation > orders". So one way to make ECLAIR happy is to change this code: > > 1) > func1(param1, func2(a), func3(b); > > into this code: > > 2) > param2 = func2(a); > param3 = func3(b); > func1(param1, param2, param3); > > Rule 13.2 is not asking us to change 1) into 2). 1) is acceptable. It is > just that ECLAIR cannot help us ensure that 1) is compliant with Rule > 13.2. It is totally fine to accept new code written in the form 1), of > course only if "the value of an expression and its persistent > side-effects shall be the same under all permitted evaluation orders". > It would likely increase the number of ECLAIR cautions, but it is not > necessarily a problem, and the ECLAIR Gitlab job will not fail. > > If one of the reviewers discovers that 1) doesn't comply with Rule 13.2 > due to manual review, then they should ask the contributor to change the > code. That is a good idea because we wouldn't want the value of an > expression to be dependant on the evaluation order which GCC cannot > guarantee. Okay, if that is our interpretation of the rule for practical purposes, then I'm no longer concerned. Jan
diff --git a/docs/misra/rules.rst b/docs/misra/rules.rst index 7b366edb07..ef60e9a455 100644 --- a/docs/misra/rules.rst +++ b/docs/misra/rules.rst @@ -462,6 +462,15 @@ maintainers if you want to suggest a change. - Initializer lists shall not contain persistent side effects - + * - `Rule 13.2 <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_13_02.c>`_ + - Required + - The value of an expression and its persistent side-effects shall + be the same under all permitted evaluation orders + - Be aware that the static analysis tool Eclair might report + several findings for Rule 13.2 of type "caution". These are + instances where Eclair is unable to verify that the code is valid + in regard to Rule 13.2. Caution reports are not violations. + * - `Rule 13.6 <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_13_06.c>`_ - Required - The operand of the sizeof operator shall not contain any @@ -583,6 +592,15 @@ maintainers if you want to suggest a change. submitting new patches please try to decrease the number of violations when possible. + * - `Rule 18.2 <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_18_02.c>`_ + - Required + - Subtraction between pointers shall only be applied to pointers + that address elements of the same array + - Be aware that the static analysis tool Eclair might report + several findings for Rule 18.2 of type "caution". These are + instances where Eclair is unable to verify that the code is valid + in regard to Rule 18.2. Caution reports are not violations. + * - `Rule 18.3 <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_18_03.c>`_ - Required - The relational operators > >= < and <= shall not be applied to objects of pointer type except where they point into the same object
Add MISRA C rules 13.2 and 18.2 to rules.rst. Both rules have zero violations reported by Eclair but they have some cautions. We accept both rules and for now we'll enable scanning for them in Eclair but only violations will cause the Gitlab CI job to fail (cautions will not.) Signed-off-by: Stefano Stabellini <stefano.stabellini@amd.com>