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Re: [RFC PATCH 4/4] automation/eclair: add deviation for certain backwards goto



Hi Julien,

On 2023-11-07 13:44, Julien Grall wrote:
Hi Nicola,

On 07/11/2023 10:33, Nicola Vetrini wrote:
As explained in the deviation record, code constructs such as
"goto retry" and "goto again" are sometimes the best balance between
code complexity and the understandability of the control flow
by developers; as such, these construct are allowed to deviate
from Rule 15.2.

Signed-off-by: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
---
  automation/eclair_analysis/ECLAIR/deviations.ecl | 10 ++++++++++
  docs/misra/deviations.rst                        | 10 ++++++++++
  2 files changed, 20 insertions(+)

diff --git a/automation/eclair_analysis/ECLAIR/deviations.ecl b/automation/eclair_analysis/ECLAIR/deviations.ecl
index fa56e5c00a27..8b1f622f8f82 100644
--- a/automation/eclair_analysis/ECLAIR/deviations.ecl
+++ b/automation/eclair_analysis/ECLAIR/deviations.ecl
@@ -270,6 +270,16 @@ statements are deliberate"
-config=MC3R1.R14.3,statements={deliberate , "wrapped(any(),node(if_stmt))" }
  -doc_end
  +#
+# Series 15
+#
+
+-doc_begin="The additional complexity introduced in the code by using control flow structures other than backwards goto-s +were deemed not to justify the possible prevention of developer confusion, given the very torough review process estabilished

Typoes: s/torough/thorough/ s/estabilished/established/


Thanks

+in the community."
+-config=MC3R1.R15.2,reports+={deliberate, "any_area(any_loc(text(^.*goto (again|retry).*$)))"}
+-doc_end
+
  #
  # Series 20.
  #
diff --git a/docs/misra/deviations.rst b/docs/misra/deviations.rst
index 8511a189253b..7d1e1f0d09b3 100644
--- a/docs/misra/deviations.rst
+++ b/docs/misra/deviations.rst
@@ -208,6 +208,16 @@ Deviations related to MISRA C:2012 Rules:
         statements are deliberate.
       - Project-wide deviation; tagged as `disapplied` for ECLAIR.
  +   * - R15.2
+ - The possible prevention of developer confusion as a result of using + control flow structures other than backwards goto-s in some instances was + deemed not strong enough to justify the additional complexity introduced + in the code. Such instances are the uses of the following labels:
+
+       - again
+       - retry

Have you investigated the possibility to use SAF-X in the code? If so, what's the problem to use them?

Cheers,

This is another viable option: putting the SAF comment on top of the label should suffice,
as shown below:

/* SAF-2-safe */
repeat:
    ++fmt;          /* this also skips first '%' */
    switch (*fmt) {
    case '-': flags |= LEFT; goto repeat;
    case '+': flags |= PLUS; goto repeat;
    case ' ': flags |= SPACE; goto repeat;
    case '#': flags |= SPECIAL; goto repeat;
    case '0': flags |= ZEROPAD; goto repeat;
    }

I think it ultimately boils down to whether Xen wants to promote the use of certain labels as the designated alternative when no other control flow mechanism is clearer from a readability perspective (in which case there should be a consistent naming to capture and deviate all of them, such as "retry") or do so on a case-by-case basis with a SAF, which is ok, but then it needs someone to check each one and either fix them or mark them as ok. Yet another route could be to mark with a SAF all those present right now to establish a baseline.

--
Nicola Vetrini, BSc
Software Engineer, BUGSENG srl (https://bugseng.com)



 


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