Re: [PATCH] Tab completion for ALTER DATABASE … SET TABLESPACE

Andres Freund <andres(at)anarazel(dot)de> writes:
> On 2018-09-21 18:00:35 -0400, Tom Lane wrote:
>> If you want to rename it, then to what? VA_ARGS_NARGS, perhaps?

> I like your suggestion. I mainly didn't like the PP_ prefix.

Sold. The original author overcomplicated it anyway; I now have

/*
* VA_ARGS_NARGS
* Returns the number of macro arguments it is passed.
*
* An empty argument still counts as an argument, so effectively, this is
* "one more than the number of commas in the argument list".
*
* This works for up to 63 arguments. Internally, VA_ARGS_NARGS_() is passed
* 64+N arguments, and the C99 standard only requires macros to allow up to
* 127 arguments, so we can't portably go higher. The implementation is
* pretty trivial: VA_ARGS_NARGS_() returns its 64th argument, and we set up
* the call so that that is the appropriate one of the list of constants.
*/
#define VA_ARGS_NARGS(...) \
VA_ARGS_NARGS_(__VA_ARGS__, \
63,62,61,60, \
59,58,57,56,55,54,53,52,51,50, \
49,48,47,46,45,44,43,42,41,40, \
39,38,37,36,35,34,33,32,31,30, \
29,28,27,26,25,24,23,22,21,20, \
19,18,17,16,15,14,13,12,11,10, \
9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
#define VA_ARGS_NARGS_( \
_01,_02,_03,_04,_05,_06,_07,_08,_09,_10, \
_11,_12,_13,_14,_15,_16,_17,_18,_19,_20, \
_21,_22,_23,_24,_25,_26,_27,_28,_29,_30, \
_31,_32,_33,_34,_35,_36,_37,_38,_39,_40, \
_41,_42,_43,_44,_45,_46,_47,_48,_49,_50, \
_51,_52,_53,_54,_55,_56,_57,_58,_59,_60, \
_61,_62,_63, N, ...) \
(N)

from which it's pretty obvious that this really is a simple macro
call. I'd first thought it involved macro recursion, but it doesn't.

> You earlier were talking about tackling this - do you still want to? I
> can otherwise, but it'll not be today, but likely tomorrow.

On it now.

regards, tom lane