Re: [PATCH] Magic block for modules

On Mon, May 08, 2006 at 10:32:47AM -0400, Tom Lane wrote:
> Martijn van Oosterhout <kleptog@svana.org> writes:
> > I was trying to find variables that when changed would make some things
> > corrupt. For example, a changed NAMEDATALEN will make any use of the
> > syscache a source of errors. A change in INDEX_MAX_KEYS will break the
> > GiST interface, etc.
>
> By that rationale you'd have to record just about every #define in the
> system headers.  And it still wouldn't be bulletproof --- what of
> custom-modified code with, say, extra fields inserted into some widely
> used struct?

I can see that. That's why I specifically aimed at the ones defined in
pg_config_manual.h, ie, the ones marked "twiddle me".

> ... So checking for identical catversion won't
> accomplish much except to force additional recompile churn on people
> doing development against CVS HEAD.  The original proposal was just
> to check for major PG version match.

Ok, I've taken out CATVERSION and cut PG version to just the major
version. I've also dropped the compiler and several others.

> Another problem with an expansive list of stuff-to-check is where does
> the add-on module find it out from?

All these symbols are defined by including c.h only, which is included
by postgres.h, so this is not an issue. I obviously didn't include any
symbols that a module would need to add special includes for. The only
outlier was CATVERSION but we're dropping that test.

> I think that will just mean that we'll break every module at the start
> of 8.2 freeze ;-).  Unless we forget to change it to error, which IMHO
> is way too likely.

Ok, one week then. Not everyone follows -patches and will be mighty
confused when a CVS update suddenly breaks everything.

Have a nice day,
--
Martijn van Oosterhout   <kleptog@svana.org>   http://svana.org/kleptog/
> From each according to his ability. To each according to his ability to litigate.