I wrote:
> Admittedly this is all moot unless some other extension starts
> using EEOP_PARAM_CALLBACK, and I didn't find any evidence of that
> using Debian Code Search. But I don't want to think of
> EEOP_PARAM_CALLBACK as being specifically tied to PL/pgSQL.
However ... given that I failed to find any outside users today,
I'm warming to the idea of "void *paramarg[2]". That does look
less random than two separate fields. There are probably not
any extensions that would need to change their code, and even
if there are, we impose bigger API breaks than this one in
every major release.
So I'm willing to do that if it satisfies your concern.
regards, tom lane