[XEN PATCH][for-4.19] xen/include: make enum perfcounter anonymous

[Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>]

Using enumerators declared in a named enum, such as the one modified,
as operands to arithmetic operators is not allowed by MISRA C:2012 Rule 10.1.
The enumerators of an anonymous enum can be used instead.

Signed-off-by: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
---
This violation manifeststs itself, for instance, in all uses of macro
'perfc_incra' from xen/include/xen/perfc.h, because the expansion
contains an arithmetic operation on two enum constants from enum perfcounter.

( (*nr) <= PERFC_LAST_hypercalls - PERFC_hypercalls ?  [...]

---
 docs/misra/rules.rst    | 3 +++
 xen/include/xen/perfc.h | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/docs/misra/rules.rst b/docs/misra/rules.rst
index 3139ca7ae6dd..26c3ff819948 100644
--- a/docs/misra/rules.rst
+++ b/docs/misra/rules.rst
@@ -341,6 +341,9 @@ maintainers if you want to suggest a change.
            compilers' extensions)
          - Implicit conversions to boolean for conditionals (?: if while
            for) and logical operators (! || &&)
+         - The essential type model allows the constants defined by anonymous
+           enums (e.g., enum { A, B, C }) to be used as operands to arithmetic
+           operators, as they have a signed essential type.

    * - `Rule 10.2 
<https://gitlab.com/MISRA/MISRA-C/MISRA-C-2012/Example-Suite/-/blob/master/R_10_02.c>`_
      - Required
diff --git a/xen/include/xen/perfc.h b/xen/include/xen/perfc.h
index 7c5ce537bd02..96022c07481e 100644
--- a/xen/include/xen/perfc.h
+++ b/xen/include/xen/perfc.h
@@ -39,7 +39,7 @@
 #define PERFSTATUS       PERFCOUNTER
 #define PERFSTATUS_ARRAY PERFCOUNTER_ARRAY

-enum perfcounter {
+enum {
 #include <xen/perfc_defn.h>
        NUM_PERFCOUNTERS
 };
--
2.34.1