From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>,
        Andres Freund <andres@anarazel.de>
Subject: Re: pg_dump versus ancient server versions
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Comments: In-reply-to Robert Haas <robertmhaas@gmail.com>
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Date: Fri, 22 Oct 2021 19:48:13 -0400
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Robert Haas <robertmhaas@gmail.com> writes:
> Another thing to think about in that regard: how likely is that
> PostgreSQL 7.4 and PostgreSQL 15 both compile and run on the same
> operating system? I suspect the answer is "not very." I seem to recall
> Greg Stark trying to compile really old versions of PostgreSQL for a
> conference talk some years ago, and he got back to a point where it
> just became impossible to make work on modern toolchains even with a
> decent amount of hackery.

Right.  The toolchains keep moving, even if the official language
definition doesn't.  For grins, I just checked out REL8_4_STABLE
on my M1 Mac, and found that it only gets this far:

checking test program... ok
checking whether long int is 64 bits... no
checking whether long long int is 64 bits... no
configure: error: Cannot find a working 64-bit integer type.

which turns out to be down to a configure-script issue we fixed
some years ago, ie using exit() without a prototype:

conftest.c:158:3: error: implicitly declaring library function 'exit' with=
 type\
 'void (int) __attribute__((noreturn))' [-Werror,-Wimplicit-function-decla=
ratio\
n]
  exit(! does_int64_work());
  ^

I notice that the configure script is also selecting some warning
switches that this compiler doesn't much like, plus it doesn't
believe 2.6.x flex is usable.  So that's *at least* three things
that'd have to be hacked even to get to a successful configure run.

Individually such issues are (usually) not very painful, but when
you have to recreate all of them at once it's a daunting project.

So if I had to rebuild 8.4 from scratch right now, I would not be
a happy camper.  That seems like a good argument for not deeming
it to be something we still have to support.

			regards, tom lane