[eesmith]

MISRA 2004, Rule 14.7: "A function shall have a single point of exit at the end of the function.", required - https://www.ibm.com/docs/en/rtr/9.0.0?topic=review-code-misr...

MISRA 2012, Rule 15.5: "Only one exit point should be defined in a function.", advisory - https://www.ibm.com/docs/en/rtr/9.0.0?topic=review-code-misr...

HN users cordenr and bfrog say it was dropped in MISRA 2023: https://news.ycombinator.com/item?id=38680587 and https://news.ycombinator.com/item?id=38704631 . Both in a recent thread on MISRA 2023 at https://news.ycombinator.com/item?id=38674158 .

FWIW, HN user FirmwareBurner in that thread links to the "Embedded System development Coding Reference guide" version 3.0 (2018) from the Software Reliability Enhancement Center, Japan at https://www.ipa.go.jp/publish/qv6pgp00000011mh-att/000065271... which says

  M3.1.5:
   A function shall end with one return statement.
   A return statement to return in the middle of processing shall
   be written only in case of recovery from abnormality.

[tirpen]

I was not aware of the changes in MISRA-2023, thanks for informing me!

Also, that's great news to hear in case I ever want to go back to the automotive industry. :)

[WesolyKubeczek]

Well, aren't early returns in guard clauses "recovery from abnormality"?

You could flex some language lawyering to define "abnormality"...

[eesmith]

I don't know.

Here is the only relevant example I found:

  p = X_MALLOC(sizeof(*p) * NUM);
  if (p == NULL) {
    return (MEM_NOTHING);
  }
  ...
  X_FREE(p);
  return (OK);

It's clearly abnormal.

Something like a:

   if (get_size(obj) == 0) {
       return empty_case;
   }
   ... do more complicated code here ...
   return result;

does not feel "abnormal", which are things you likely want to log, given:

   Logs should be output not only when an abnormal condition
   is detected, but also at the timing of, such as, data 
   communication with an external system.

[aulin]

I believe that's exactly it. An exception to the single return rule to allow for guard clauses. Wording is maybe a little too obscure though.