clang-format and PenaltyReturnTypeOnItsOwnLine?

Clang Frontend
#1

Hi all,

Hope this is the right channel for this question :). I'm looking at possibly using clang-format to clean up an indentation / formatting style mess for a fairly large project (Apache Traffic Server). One of our "quirks" is that we currently format our functions like:

inline const char*
some_func(int some_arg)
{
    …
}

I've tried both

  PenaltyReturnTypeOnItsOwnLine: 0

and

  PenaltyReturnTypeOnItsOwnLine: 10000

and various numbers in between, but it always formats the above like

inline const char* some_func(int some_arg)
{
  …
}

Maybe I'm misunderstanding what PenaltyReturnTypeOnItsOwnLine does? What's even more confusing is that if I use the "mozilla" predefined format, it still doesn't format it like I expect. And I'm 99% certain that Mozilla code also uses the "return type on its own line" formatting.

Cheers!

-- leif

#2

Hi all,

Hope this is the right channel for this question :). I’m looking at possibly using clang-format to clean up an indentation / formatting style mess for a fairly large project (Apache Traffic Server). One of our “quirks” is that we currently format our functions like:

inline const char*
some_func(int some_arg)
{
…
}

I’ve tried both

PenaltyReturnTypeOnItsOwnLine: 0

and

PenaltyReturnTypeOnItsOwnLine: 10000

and various numbers in between, but it always formats the above like

inline const char* some_func(int some_arg)
{
…
}

Maybe I’m misunderstanding what PenaltyReturnTypeOnItsOwnLine does?

I assume it identifies the 'cost of splitting a line after the return. Relative costs of different splits are used in comparisons to decide on the optimal split - I doubt it’ll change anything related to the behavior of the unsplit lines.

#3

Yes, clang-format currently does not have an option that says “always break after a function’s return type”. It should be fairly easy to add, though. Does your coding style prescribe this for definitions only or also for declarations?

#4

Yes, clang-format currently does not have an option that says "always break after a function's return type". It

Ah, alright, so at least I'm not doing it wrong :).

should be fairly easy to add, though. Does your coding style prescribe this for definitions only or also for declarations?

Definitions only.

Cheers,

-- Leif

#5

Sorry for not following up on this. Is it worth filing an RFE issue on this? Is it something that others than just me would find useful? Is this a feature that a mere mortal (like me…) could contribute?

Cheers,

-- Leif

#6

>
>> Yes, clang-format currently does not have an option that says "always
break after a function's return type". It
>
> Ah, alright, so at least I'm not doing it wrong :).
>
>> should be fairly easy to add, though. Does your coding style prescribe
this for definitions only or also for declarations?
>
>
> Definitions only.

Sorry for not following up on this. Is it worth filing an RFE issue on
this? Is it something that others than just me would find useful?

I don't know. I have not seen coding style that do this, but I don't doubt
that they exist.

Is this a feature that a mere mortal (like me…) could contribute?

I don't see why not. Basically you need to add a corresponding if-statement
to TokenAnnotator::calculateFormattingInformation()
(lib/Format/TokenAnnotator.cpp) that sets MustBreakBefore of the first
Token of the function name accordingly. The if-statement itself is probably
quite similar to the code-path the returns
Style.PenaltyReturnTypeOnItsOwnLine in TokenAnnotator::splitPenalty(). All
that would need to be guarded by a new style flag of type bool (see r188793
for an example of how to add additional flags).

Cheers,