Re: "WARNING: parenthesis in function name" correctness

[Yuri Pankov <yuripv@yuripv.net>]

Ingo Schwarze wrote:
> Hi Yuri,
> 
> Yuri Pankov wrote on Tue, Sep 10, 2019 at 11:20:24AM +0300:
> 
>> I'm looking into fixing sbuf.9 which currently has somewhat unreadable:
>>
>> .Ft typedef\ int ( sbuf_drain_func ) ( void\ *arg, const\ char\ *data,
>> int\ len ) ;
> 
> Indeed, that is horrible and should be fixed.
> 
>> ...into somewhat nicer:
>>
>> .Ft typedef int
>> .Fo (sbuf_drain_func)
>> .Fa "void *arg"
>> .Fa "const char *data"
>> .Fa "int len"
>> .Fc
>>
>> ...but that gives me a:
>>
>> mandoc: share/man/man9/sbuf.9:69:5: WARNING: parenthesis in function
>> name: (sbuf_drain_func)
>>
>> Looking at the code, parenthesis are only allowed in the following form:
>>
>> .Ft (*func_ptr)
> 
> I think you mean .Fo/.Fn, not .Ft, right?

Yes, I was thinking about .Fo, sorry.

>> ...while here we don't have a "*" -- it's the way it's typedef'ed in the
>> source, and I want to follow it, so I wonder if that check/warning is
>> really useful.
> 
> If i understand the C standard correctly (otherwise, please somebody
> correct me!), we have:
> 
>    int (f)()    --  function returning int
>    int (*fp)()  --  pointer to function returning int
> 
> In many situations, both can be used interchangeably, consider for
> example C89 3.2.2.1: "A function designator is an expression that
> has function type.  Except when it is the operand of the sizeof
> operator or the unary & operator, a function designator with type
> ``function returning type'' is converted to an expression that has
> type ``pointer to function returning type.''"
> 
> Then again, it seems for sizeof(), it may make a difference whether
> a type is a function type or a function pointer type, and maybe there
> are also other situations where that matters.
> 
> So i suspect you are right there are legitimate reasons for making
> the difference in the documentation, too,
> and saying ".Fo (sbuf_drain_func)" looks reasonable.
> Do others agree?
> 
> I plan to suppress the warning for ".Fo (f)" just like for ".Fo (*f)"
> in the future.  The likely typo that should be warned about
> is ".Fo f()", and that warning will still work.

Sounds good, thank you!
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