Re: Variable-length FunctionCallInfoData

Hi,

Here's an updated version of the patch. Besides a rebase the biggest
change is that I've wrapped:

On 2018-06-05 10:29:52 -0700, Andres Freund wrote:
> There's some added uglyness, which I hope we can polish a bit
> further. Right now we allocate a good number of FunctionCallInfoData
> struct on the stack - which doesn't quite work afterwards anymore. So
> the stack allocations, for the majoroity cases where the argument number
> is known, currently looks like:
>
> union {
> FunctionCallInfoData fcinfo;
> char *fcinfo_data[SizeForFunctionCallInfoData(0)];
> } fcinfodata;
> FunctionCallInfo fcinfo = &fcinfodata.fcinfo;
>
> that's not pretty, but also not that bad.

into a macro STACK_FCINFO_FOR_ARGS(varname, numargs). That makes the
code look much nicer.

I think we should go for this. If there's some agreement on that I'll
perform a bit more polishing.

I think it'd probably good to add accessors for value/nullness in
arguments that hide the difference between <v12 and v12, for the sake of
extension authors. Would probably mostly make sense if we backpatched
those for compatibility.

Also attached is a second patch that avoids all the duplication in
fmgr.[ch]. While the savings are nice, I'm a bit doubtful that the
amount of magic here is reasonable. Any opinions?

Greetings,

Andres Freund