From: Tom Lane <tgl@sss.pgh.pa.us>
To: clemens.ruck@t-online.de
cc: pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #19518: Path resolution for loading a function fails,
 if postgres is somewhere in the path.
In-reply-to: <19518-902fabd6a225851f@postgresql.org>
References: <19518-902fabd6a225851f@postgresql.org>
Comments: In-reply-to PG Bug reporting form <noreply@postgresql.org>
	message dated "Fri, 12 Jun 2026 19:19:31 -0000"
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Date: Fri, 12 Jun 2026 20:52:09 -0400
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PG Bug reporting form <noreply@postgresql.org> writes:
> I encountered an incorrect $libdir expansion when loading a C-language
> function from a shared library.

I'm not sure if this is just a typo in your submission,
but:

> CREATE OR REPLACE FUNCTION test(integer)
> RETURNS integer
> AS '$libdir/../../../hol-lambdas/src/ext/l_udfs.so',
>    'l_test'
> LANGUAGE C
> STRICT;

This is looking for l_udfs.so, but the rest of your message
references lambda_udfs.so.  That wouldn't be the cause would it?

> The issue depends on the surrounding directory names. With the PostgreSQL
> repository located under a differently named directory, the same build and
> SQL statement resolve the expected path.

The presence of "postgres" in the --prefix string affects whether
our Makefile.global decides to append an extra directory level to
pkglib_path:

pkglibdir = $(libdir)
ifeq "$(findstring pgsql, $(pkglibdir))" ""
ifeq "$(findstring postgres, $(pkglibdir))" ""
override pkglibdir := $(pkglibdir)/postgresql
endif
endif

That is, with your specified

    --prefix=/home/testuser/projects/hol-postgres/install

the pkglib_path would be

    /home/testuser/projects/hol-postgres/install/lib

but with, say,

    --prefix=/home/testuser/projects/hol-postgrex/install

the pkglib_path would be

    /home/testuser/projects/hol-postgrex/install/lib/postgresql

thus changing the number of ".."s needed in your example.  Perhaps
that rule explains your results with different installation paths?

> I can provide the exact compiled values of PGBINDIR and PKGLIBDIR, the
> resulting runtime pkglib_path, and a patch or regression test if required.

I'm quite hesitant to change the behavior around this: it's stood for
decades and any change would certainly break a bunch of people's
build/install recipes.

			regards, tom lane