Add D4.12 with the same explanation as the rules of the R21 series.
D4.12 refers to the standard library memory allocation functions and
similar third party libraries with memory allocation functions. It
doesn't refer to the in-tree implementation we have in Xen which is
subject to MISRA C rules and MISRA C scanning.

Signed-off-by: Stefano Stabellini <stefano.stabellini@amd.com>

diff --git a/docs/misra/rules.rst b/docs/misra/rules.rst
index 80e5e972ad..bc8506add4 100644
--- a/docs/misra/rules.rst
+++ b/docs/misra/rules.rst
@@ -76,6 +76,11 @@ maintainers if you want to suggest a change.
        considered libraries from MISRA C point of view as they are
        imported in source form)
 
+   * - `Dir 4.12 <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/D_04_12.c>`_
+     - Required
+     - Dynamic memory allocation shall not be used
+     - Xen doesn't provide, use, or link against a Standard Library [#xen-stdlib]_
+
    * - `Dir 4.14 <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/D_04_14.c>`_
      - Required
      - The validity of values received from external sources shall be

On 15.05.2024 01:15, Stefano Stabellini wrote:
> Add D4.12 with the same explanation as the rules of the R21 series.
> D4.12 refers to the standard library memory allocation functions and
> similar third party libraries with memory allocation functions. It
> doesn't refer to the in-tree implementation we have in Xen which is
> subject to MISRA C rules and MISRA C scanning.
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@amd.com>
> 
> diff --git a/docs/misra/rules.rst b/docs/misra/rules.rst
> index 80e5e972ad..bc8506add4 100644
> --- a/docs/misra/rules.rst
> +++ b/docs/misra/rules.rst
> @@ -76,6 +76,11 @@ maintainers if you want to suggest a change.
>         considered libraries from MISRA C point of view as they are
>         imported in source form)
>  
> +   * - `Dir 4.12 <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/D_04_12.c>`_
> +     - Required
> +     - Dynamic memory allocation shall not be used
> +     - Xen doesn't provide, use, or link against a Standard Library [#xen-stdlib]_

I'm having trouble connecting this remark with the directive. We do have
dynamic memory allocation routines, and we use them. It doesn't really
matter that they don't come from an external library, does it?

Jan

On Wed, 15 May 2024, Jan Beulich wrote:
> On 15.05.2024 01:15, Stefano Stabellini wrote:
> > Add D4.12 with the same explanation as the rules of the R21 series.
> > D4.12 refers to the standard library memory allocation functions and
> > similar third party libraries with memory allocation functions. It
> > doesn't refer to the in-tree implementation we have in Xen which is
> > subject to MISRA C rules and MISRA C scanning.
> > 
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@amd.com>
> > 
> > diff --git a/docs/misra/rules.rst b/docs/misra/rules.rst
> > index 80e5e972ad..bc8506add4 100644
> > --- a/docs/misra/rules.rst
> > +++ b/docs/misra/rules.rst
> > @@ -76,6 +76,11 @@ maintainers if you want to suggest a change.
> >         considered libraries from MISRA C point of view as they are
> >         imported in source form)
> >  
> > +   * - `Dir 4.12 <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/D_04_12.c>`_
> > +     - Required
> > +     - Dynamic memory allocation shall not be used
> > +     - Xen doesn't provide, use, or link against a Standard Library [#xen-stdlib]_
> 
> I'm having trouble connecting this remark with the directive. We do have
> dynamic memory allocation routines, and we use them. It doesn't really
> matter that they don't come from an external library, does it?

Similarly to the 21.x rules series, it makes a difference if they are
external libraries or code within the project. The rule points out that
the standard library memory allocation functions can lead to undefined
behavior. On the other hand, our own implementation under xen.git is
subject to MISRA C scanning and all the other MISRA C rules.

The example in the link above, shows a use-after-free error that in our
case it should be caught by other MISRA C rules scanning.

On Wed, 15 May 2024, Stefano Stabellini wrote:
> On Wed, 15 May 2024, Jan Beulich wrote:
> > On 15.05.2024 01:15, Stefano Stabellini wrote:
> > > Add D4.12 with the same explanation as the rules of the R21 series.
> > > D4.12 refers to the standard library memory allocation functions and
> > > similar third party libraries with memory allocation functions. It
> > > doesn't refer to the in-tree implementation we have in Xen which is
> > > subject to MISRA C rules and MISRA C scanning.
> > > 
> > > Signed-off-by: Stefano Stabellini <stefano.stabellini@amd.com>
> > > 
> > > diff --git a/docs/misra/rules.rst b/docs/misra/rules.rst
> > > index 80e5e972ad..bc8506add4 100644
> > > --- a/docs/misra/rules.rst
> > > +++ b/docs/misra/rules.rst
> > > @@ -76,6 +76,11 @@ maintainers if you want to suggest a change.
> > >         considered libraries from MISRA C point of view as they are
> > >         imported in source form)
> > >  
> > > +   * - `Dir 4.12 <https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/D_04_12.c>`_
> > > +     - Required
> > > +     - Dynamic memory allocation shall not be used
> > > +     - Xen doesn't provide, use, or link against a Standard Library [#xen-stdlib]_
> > 
> > I'm having trouble connecting this remark with the directive. We do have
> > dynamic memory allocation routines, and we use them. It doesn't really
> > matter that they don't come from an external library, does it?
> 
> Similarly to the 21.x rules series, it makes a difference if they are
> external libraries or code within the project. The rule points out that
> the standard library memory allocation functions can lead to undefined
> behavior. On the other hand, our own implementation under xen.git is
> subject to MISRA C scanning and all the other MISRA C rules.
> 
> The example in the link above, shows a use-after-free error that in our
> case it should be caught by other MISRA C rules scanning.

Just to close the loop on this -- I spoke with Roberto about D4.12, and
we decided that it is best to leave out this directive for now.