Feedback-ID: id4a34324:Fastmail
Date: Mon, 11 Jul 2022 14:37:55 -0700
From: Andres Freund <andres@anarazel.de>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Robert Haas <robertmhaas@gmail.com>,
	Peter Eisentraut <peter.eisentraut@enterprisedb.com>,
	David Rowley <dgrowleyml@gmail.com>,
	pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: automatically generating node support functions
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Hi,

On 2022-07-11 16:38:05 -0400, Tom Lane wrote:
> Andres Freund <andres@anarazel.de> writes:
> > On 2022-07-11 15:54:22 -0400, Tom Lane wrote:
> >> We can't simply move the file list into gen_node_support.pl, because
> >> (a) the build system has to know about the dependencies involved
> 
> > Meson has builtin support for tools like gen_node_support.pl reporting which
> > files they've read and then to use those as dependencies. It'd not be a lot of
> > effort to open-code that with make either.
> 
> If you want to provide code for that, sure, but I don't know how to do it.

It'd basically be something like a --deps option providing a path to a file
(e.g. .deps/nodetags.Po) where the script would emit something roughly
equivalent to

path/to/nodetags.h: path/to/nodes/nodes.h
path/to/nodetags.h: path/to/nodes/primnodes.h
...
path/to/readfuncs.c: path/to/nodetags.h

It might or might not make sense to output this as one rule instead of
multiple ones.

I think our existing dependency support would do the rest.


We'd still need a dependency on node-support-stamp (or nodetags.h or ...), to
trigger the first invocation of gen_node_support.pl.


I don't think it's worth worrying about this not working reliably for non
--enable-depend builds, there's a lot more broken than this. But it might be a
bit annoying to deal with either a) creating the .deps directory even without
--enable-depend, or b) specifying --deps only optionally.

I can give it a go if this doesn't sound insane.

Greetings,

Andres Freund