v1-0001-Fix-Don-t-strip-libdir-from-nested-module_pathnam.patch

From b08f54adddc0beaa79a330dd3c9e2f3ff25b3d08 Mon Sep 17 00:00:00 2001
From: Matheus Alcantara <mths.dev@pm.me>
Date: Fri, 22 Aug 2025 10:23:31 -0300
Subject: [PATCH v1] Fix: Don't strip $libdir from nested module_pathnames

This patch fixes a bug in how 'load_external_function' handles
'$libdir/ prefixes in module paths.

Previously, 'load_external_function' would unconditionally strip
'$libdir/' from the beginning of the 'filename' string. This
caused an issue when the path was nested, such as "$libdir/nested/my_lib".
Stripping the prefix resulted in a path of "nested/my_lib", which would
fail to be found by the expand_dynamic_library_name function because
the original '$libdir' macro was removed.

To fix this, the code now checks for the presence of an additional
directory separator ('/' or '\') after the '$libdir/' prefix. The prefix
is only stripped if the remaining string does not contain a separator.
This ensures that simple filenames like '"$libdir/my_lib"' are correctly
handled, while nested paths are left intact for 'expand_dynamic_library_name'
to process correctly.

Reported By: Dilip Kumar
Author: Matheus Alcantara
Author: Dilip Kumar
Reviewer: Srinath Reddy Sadipiralla
---
 src/backend/utils/fmgr/dfmgr.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/src/backend/utils/fmgr/dfmgr.c b/src/backend/utils/fmgr/dfmgr.c
index 4bb84ff7087..d39966829fd 100644
--- a/src/backend/utils/fmgr/dfmgr.c
+++ b/src/backend/utils/fmgr/dfmgr.c
@@ -100,12 +100,19 @@ load_external_function(const char *filename, const char *funcname,
 	void	   *retval;
 
 	/*
-	 * If the value starts with "$libdir/", strip that.  This is because many
-	 * extensions have hardcoded '$libdir/foo' as their library name, which
-	 * prevents using the path.
+	 * For extensions with hardcoded '$libdir/' library names, we strip the
+	 * prefix to allow the library search path to be used. This is done only
+	 * for simple names (e.g., "$libdir/foo"), not for nested paths
+	 * (e.g., "$libdir/foo/bar").
+	 *
+	 * For nested paths, 'expand_dynamic_library_name' directly expands the
+	 * '$libdir' macro, so we leave them untouched.
 	 */
 	if (strncmp(filename, "$libdir/", 8) == 0)
-		filename += 8;
+	{
+		if (first_dir_separator(filename + 8) == NULL)
+			filename += 8;
+	}
 
 	/* Expand the possibly-abbreviated filename to an exact path name */
 	fullname = expand_dynamic_library_name(filename);
-- 
2.51.0.261.g7ce5a0a67e-goog