From: Tom Lane <tgl@sss.pgh.pa.us>
To: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
cc: Andres Freund <andres@anarazel.de>,
        pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: warnings for invalid function casts
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Comments: In-reply-to Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
	message dated "Fri, 03 Jul 2020 16:04:10 +0200"
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Date: Fri, 03 Jul 2020 10:40:00 -0400
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Peter Eisentraut <peter.eisentraut@2ndquadrant.com> writes:
> On 2020-06-30 21:38, Tom Lane wrote:
>> In any case, I think the issue here is what is the escape hatch for saying
>> that "I know this cast is okay, don't warn about it, thanks".  Treating
>> "void (*) (void)" as special for that purpose is nothing more nor less
>> than a kluge, so another compiler might do it differently.  Given the
>> POSIX restriction, I think we could reasonably use "void *" instead.

> I think gcc had to pick some escape hatch that is valid also outside of 
> POSIX, so they just had to pick something.  If we're disregarding 
> support for these Harvard architecture type things, then we might as 
> well use void * for easier notation.

As long as it's behind a typedef, the code will look the same in any
case ;-).

> Btw., one of the hunks in my patch was in PL/Python.  I have found an 
> equivalent change in the core Python code, which does make use of void 
> (*) (void): https://github.com/python/cpython/commit/62be74290aca

Given that gcc explicitly documents "void (*) (void)" as being what
to use, they're going to have a hard time changing their minds about
that ... and gcc is dominant enough in this space that I suppose
other compilers would have to be compatible with it.  So even though
it's theoretically bogus, I suppose we might as well go along with
it.  The typedef will allow a centralized fix if we ever find a
better answer.

			regards, tom lane