Re: Proposal: Document ABI Compatibility

On 12.06.24 16:47, Robert Haas wrote:
> On Mon, Jun 3, 2024 at 3:39 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Me either.  There are degrees of ABI compatibility
> 
> Exactly this!
> 
> What I think would be useful to document is our usual practices e.g.
> adding new struct members at the end of structs, trying to avoid
> changing public function signatures. If we document promises to
> extension authors, I don't know how much difference that will make:
> we'll probably end up needing to violate them at some point for one
> reason or another. But if we document what committers should do, then
> we might do better than we're now, because committers will be more
> likely to do it right, and extension authors can also read those
> instructions to understand what our practices are.

Fun fact:  At the end of src/tools/RELEASE_CHANGES, there is some 
guidance on how to maintain ABI compatibility in *libpq*.  That used to 
be a problem.  We have come far since then.

But yes, a bit of documentation like that (maybe not in that file 
though) would make sense.