Re: [PATCH v2] hypfs: add ASSERT_UNREACHABLE() in hypfs_get_entry_rel()

[Jan Beulich <jbeulich@xxxxxxxx>]

On 29.04.2026 11:44, Andrew Cooper wrote:
> On 28/04/2026 7:19 pm, Dmytro Prokopchuk1 wrote:
>> The statement 'return ERR_PTR(-ENOENT);' on the final line of the
>> function 'hypfs_get_entry_rel()' is unreachable because the logic within
>> the infinite loop 'for (;;)' provides all possible exit paths for the
>> function. So there is no execution path to exit the loop and reach the
>> final that statement.
>>
>> This unreachable code violates MISRA C Rule 2.1 which states: "A project
>> shall not contain unreachable code".
>>
>> To fix that and potential compilers "control reaches end of non-void
>> function" warning, mark the code path as unreachable using macro
>> 'ASSERT_UNREACHABLE()'.
>>
>> Signed-off-by: Dmytro Prokopchuk <dmytro_prokopchuk1@xxxxxxxx>
>> ---
>> Changes in v2:
>> - add ASSERT_UNREACHABLE() before the final return statement instead of 
>> removing it
>> Test CI pipeline:
>> https://gitlab.com/xen-project/people/dimaprkp4k/xen/-/pipelines/2485661910
>> Link to v1:
>> https://patchew.org/Xen/341811ced2943fb79d0235c27781c564c7bdaf02.1775749146.git.dmytro._5Fprokopchuk1@xxxxxxxx/
>> ---
>>  xen/common/hypfs.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/xen/common/hypfs.c b/xen/common/hypfs.c
>> index cdf4ee0171..02fb234568 100644
>> --- a/xen/common/hypfs.c
>> +++ b/xen/common/hypfs.c
>> @@ -348,6 +348,7 @@ static struct hypfs_entry *hypfs_get_entry_rel(struct 
>> hypfs_entry_dir *dir,
>>          dir = container_of(entry, struct hypfs_entry_dir, e);
>>      }
>>  
>> +    ASSERT_UNREACHABLE();
>>      return ERR_PTR(-ENOENT);
>>  }
>>  
> 
> No.  This is absurd.

Why?

> Not to mention that you are *definitely* not fixing the stated MISRA rule.

Correct. It is instead deviating that rule for this code instance. I'm pretty
sure we have a few other similar pieces of code elsewhere.

In any event - your reply isn't really actionable. If you want things done
differently, then please make a concrete suggestion. Otherwise, in a couple
of days, I'll commit this with Jürgen's R-b.

Jan