[PATCH v1] misra: add deviation of Rule 10.1 for unary minus

[<victorm.lira@xxxxxxx>]

From: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>

MISRA C Rule 10.1 states:
"Operands shall not be of an inappropriate essential type"

The unary minus operator applied to an unsigned quantity has
a semantics (wrap around) that is well-known to all Xen developers.
Thus, this operation is deemed safe.

No functional change.

Signed-off-by: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
Signed-off-by: Federico Serafini <federico.serafini@xxxxxxxxxxx>
Signed-off-by: Victor Lira <victorm.lira@xxxxxxx>
---
Changes v1:
- add rule title to commit message
---
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>
---
 automation/eclair_analysis/ECLAIR/deviations.ecl | 6 ++++++
 docs/misra/deviations.rst                        | 6 ++++++
 2 files changed, 12 insertions(+)

diff --git a/automation/eclair_analysis/ECLAIR/deviations.ecl 
b/automation/eclair_analysis/ECLAIR/deviations.ecl
index 303b06203a..2cfce850bd 100644
--- a/automation/eclair_analysis/ECLAIR/deviations.ecl
+++ b/automation/eclair_analysis/ECLAIR/deviations.ecl
@@ -347,6 +347,12 @@ constant expressions are required.\""
   "any()"}
 -doc_end

+-doc_begin="Unary minus operations on non-negative integers have a semantics 
(wrap around) that is well-known to all Xen developers."
+-config=MC3A2.R10.1,etypes+={safe,
+  "stmt(node(unary_operator)&&operator(minus))",
+  "src_expr(definitely_in(0..))"}
+-doc_end
+
 #
 # Series 11
 #
diff --git a/docs/misra/deviations.rst b/docs/misra/deviations.rst
index cfdd1a9838..c5897e31c5 100644
--- a/docs/misra/deviations.rst
+++ b/docs/misra/deviations.rst
@@ -321,6 +321,12 @@ Deviations related to MISRA C:2012 Rules:
        If no bits are set, 0 is returned.
      - Tagged as `safe` for ECLAIR.

+   * - R10.1
+     - Applying the unary minus operator to an unsigned quantity has a
+       semantics (wrap around) that is well-known to all Xen developers.
+       For this reason, the operation is safe.
+     - Tagged as `safe` for ECLAIR.
+
    * - R11.1
      - The conversion from a function pointer to unsigned long or (void \*) 
does
        not lose any information, provided that the target type has enough bits
--
2.47.0