Re: [XEN PATCH v5] automation/eclair: extend existing deviations of MISRA C Rule 16.3

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 20 Aug 2024, Federico Serafini wrote:
> Update ECLAIR configuration to deviate more cases where an
> unintentional fallthrough cannot happen.
> 
> Tag Rule 16.3 as clean for arm.
> 
> Signed-off-by: Federico Serafini <federico.serafini@xxxxxxxxxxx>
> ---
> Hi, v4 of this patch has been on hold due to discussion on whether or not
> to consider switch clauses ending with ASSERT_UNREACHABLE() as safe;
> I propose the patch again to continue the discussion and maybe reach an
> agreement.

Yes this makes sense and reflect the agreement reached on the other
thread

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


> ---
> Changes from v4:
> - rebase against staging.
> ---
> Changes from v3:
> - do not add the rule to the monitored set (it is already there).
> ---
> Changes from v2:
> - fixed grammar;
> - reprhased deviations regarding do-while-false and ASSERT_UNREACHABLE().
> ---
>  .../eclair_analysis/ECLAIR/deviations.ecl     | 28 +++++++++++++++----
>  automation/eclair_analysis/ECLAIR/tagging.ecl |  2 +-
>  docs/misra/deviations.rst                     | 28 +++++++++++++++++--
>  3 files changed, 48 insertions(+), 10 deletions(-)
> 
> diff --git a/automation/eclair_analysis/ECLAIR/deviations.ecl 
> b/automation/eclair_analysis/ECLAIR/deviations.ecl
> index 1aa8277066..9051f41602 100644
> --- a/automation/eclair_analysis/ECLAIR/deviations.ecl
> +++ b/automation/eclair_analysis/ECLAIR/deviations.ecl
> @@ -461,14 +461,30 @@ therefore it is deemed better to leave such files as 
> is."
>  -config=MC3R1.R16.2,reports+={deliberate, 
> "any_area(any_loc(file(x86_emulate||x86_svm_emulate)))"}
>  -doc_end
>  
> --doc_begin="Switch clauses ending with continue, goto, return statements are
> -safe."
> --config=MC3R1.R16.3,terminals+={safe, 
> "node(continue_stmt||goto_stmt||return_stmt)"}
> +-doc_begin="Statements that change the control flow (i.e., break, continue, 
> goto, return) and calls to functions that do not return the control back are 
> \"allowed terminal statements\"."
> +-stmt_selector+={r16_3_allowed_terminal, 
> "node(break_stmt||continue_stmt||goto_stmt||return_stmt)||call(property(noreturn))"}
> +-config=MC3R1.R16.3,terminals+={safe, "r16_3_allowed_terminal"}
> +-doc_end
> +
> +-doc_begin="An if-else statement having both branches ending with an allowed 
> terminal statement is itself an allowed terminal statement."
> +-stmt_selector+={r16_3_if, 
> "node(if_stmt)&&(child(then,r16_3_allowed_terminal)||child(then,any_stmt(stmt,-1,r16_3_allowed_terminal)))"}
> +-stmt_selector+={r16_3_else, 
> "node(if_stmt)&&(child(else,r16_3_allowed_terminal)||child(else,any_stmt(stmt,-1,r16_3_allowed_terminal)))"}
> +-stmt_selector+={r16_3_if_else, "r16_3_if&&r16_3_else"}
> +-config=MC3R1.R16.3,terminals+={safe, "r16_3_if_else"}
> +-doc_end
> +
> +-doc_begin="An if-else statement having an always true condition and the 
> true branch ending with an allowed terminal statement is itself an allowed 
> terminal statement."
> +-stmt_selector+={r16_3_if_true, "r16_3_if&&child(cond,definitely_in(1..))"}
> +-config=MC3R1.R16.3,terminals+={safe, "r16_3_if_true"}
> +-doc_end
> +
> +-doc_begin="A switch clause ending with a statement expression which, in 
> turn, ends with an allowed terminal statement is safe."
> +-config=MC3R1.R16.3,terminals+={safe, 
> "node(stmt_expr)&&child(stmt,node(compound_stmt)&&any_stmt(stmt,-1,r16_3_allowed_terminal||r16_3_if_else||r16_3_if_true))"}
>  -doc_end
>  
> --doc_begin="Switch clauses ending with a call to a function that does not 
> give
> -the control back (i.e., a function with attribute noreturn) are safe."
> --config=MC3R1.R16.3,terminals+={safe, "call(property(noreturn))"}
> +-doc_begin="A switch clause ending with a do-while-false the body of which, 
> in turn, ends with an allowed terminal statement is safe.
> +An exception to that is the macro ASSERT_UNREACHABLE() which is effective in 
> debug build only: a switch clause ending with ASSERT_UNREACHABLE() is not 
> considered safe."
> +-config=MC3R1.R16.3,terminals+={safe, 
> "!macro(name(ASSERT_UNREACHABLE))&&node(do_stmt)&&child(cond,definitely_in(0))&&child(body,any_stmt(stmt,-1,r16_3_allowed_terminal||r16_3_if_else||r16_3_if_true))"}
>  -doc_end
>  
>  -doc_begin="Switch clauses ending with pseudo-keyword \"fallthrough\" are
> diff --git a/automation/eclair_analysis/ECLAIR/tagging.ecl 
> b/automation/eclair_analysis/ECLAIR/tagging.ecl
> index 4d0ac94848..b8448938e6 100644
> --- a/automation/eclair_analysis/ECLAIR/tagging.ecl
> +++ b/automation/eclair_analysis/ECLAIR/tagging.ecl
> @@ -112,7 +112,7 @@ if(string_equal(target,"x86_64"),
>  )
>  
>  if(string_equal(target,"arm64"),
> -    
> service_selector({"additional_clean_guidelines","MC3R1.R16.6||MC3R1.R2.1||MC3R1.R5.3||MC3R1.R7.3"})
> +    
> service_selector({"additional_clean_guidelines","MC3R1.R2.1||MC3R1.R5.3||MC3R1.R7.3||MC3R1.R16.3||MC3R1.R16.6"})
>  )
>  
>  
> -reports+={clean:added,"service(clean_guidelines_common||additional_clean_guidelines)"}
> diff --git a/docs/misra/deviations.rst b/docs/misra/deviations.rst
> index d51aa422b5..b66c271c4e 100644
> --- a/docs/misra/deviations.rst
> +++ b/docs/misra/deviations.rst
> @@ -415,12 +415,34 @@ Deviations related to MISRA C:2012 Rules:
>       - Tagged as `deliberate` for ECLAIR.
>  
>     * - R16.3
> -     - Switch clauses ending with continue, goto, return statements are safe.
> +     - Statements that change the control flow (i.e., break, continue, goto,
> +       return) and calls to functions that do not return the control back are
> +       \"allowed terminal statements\".
>       - Tagged as `safe` for ECLAIR.
>  
>     * - R16.3
> -     - Switch clauses ending with a call to a function that does not give
> -       the control back (i.e., a function with attribute noreturn) are safe.
> +     - An if-else statement having both branches ending with one of the 
> allowed
> +       terminal statemets is itself an allowed terminal statements.
> +     - Tagged as `safe` for ECLAIR.
> +
> +   * - R16.3
> +     - An if-else statement having an always true condition and the true
> +       branch ending with an allowed terminal statement is itself an allowed
> +       terminal statement.
> +     - Tagged as `safe` for ECLAIR.
> +
> +   * - R16.3
> +     - A switch clause ending with a statement expression which, in turn, 
> ends
> +       with an allowed terminal statement (e.g., the expansion of
> +       generate_exception()) is safe.
> +     - Tagged as `safe` for ECLAIR.
> +
> +   * - R16.3
> +     - A switch clause ending with a do-while-false the body of which, in 
> turn,
> +       ends with an allowed terminal statement (e.g., PARSE_ERR_RET()) is 
> safe.
> +       An exception to that is the macro ASSERT_UNREACHABLE() which is
> +       effective in debug build only: a switch clause ending with
> +       ASSERT_UNREACHABLE() is not considered safe.
>       - Tagged as `safe` for ECLAIR.
>  
>     * - R16.3
> -- 
> 2.34.1
>