Re: [RFC PATCH 4/4] automation/eclair: add deviation for certain backwards goto
On 2023-11-07 18:35, Julien Grall wrote:
On 07/11/2023 14:45, Nicola Vetrini wrote:
Hi Julien,
Hi,
On 2023-11-07 13:44, Julien Grall wrote:
+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,
I would prefer a case-by-case basis because it adds an additional
review. With deviating by keywords, the reviewrs/developpers may not be
aware of the deviation (which may be fine for some, but IMHO not this
one).
Ok, I'll keep this in mind when the rule will be discussed.
but then
it needs someone to check each one and either fix them or mark them as
ok.
Don't we technically already need to go through all the existing use of
ready & co even if we deviate by keyword?
my hope was trying to extract a common well-known pattern that can be
defensible as a deviation and then fix the rest.
Yet another route could be to mark with a SAF all those present right
now to establish a baseline.
How many do we have?
~30 in Arm (half of which are in common code) and ~250 in x86. The
actual count of labels
is lower, because a report is given for each use of a backward jump, but
those under
x86e_emulate likely do not (~40 total on x86 remain if we exclude
x86_emulate/.*).
https://saas.eclairit.com:3787/fs/var/local/eclair/XEN.ecdf/ECLAIR_normal/arm/for-4.19/ARM64-Set3/372/PROJECT.ecd;/by_service/MC3R1.R15.2.html
https://saas.eclairit.com:3787/fs/var/local/eclair/XEN.ecdf/ECLAIR_normal/x86_64/staging/X86_64-Set3/372/PROJECT.ecd;/by_service/MC3R1.R15.2.html#
Cheers,
--
Nicola Vetrini, BSc
Software Engineer, BUGSENG srl (https://bugseng.com)
Re: [RFC PATCH 4/4] automation/eclair: add deviation for certain backwards goto
On 07/11/2023 14:45, Nicola Vetrini wrote:
Hi Julien,
Hi,
On 2023-11-07 13:44, Julien Grall wrote:
+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,
I would prefer a case-by-case basis because it adds an additional
review. With deviating by keywords, the reviewrs/developpers may not be
aware of the deviation (which may be fine for some, but IMHO not this one).
but then
it needs someone to check each one and either fix them or mark them as ok.
Don't we technically already need to go through all the existing use of
ready & co even if we deviate by keyword?
Yet another route could be to mark with a SAF all those present right
now to establish a baseline.
How many do we have?
Cheers,
--
Julien Grall
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
---
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)
Re: [RFC PATCH 4/4] automation/eclair: add deviation for certain backwards goto
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
---
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/
+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,
--
Julien Grall
