From: Chao Li <li.evan.chao@gmail.com>
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Subject: Fix a bug in extension_file_exists()
Message-Id: <362EA9B3-589B-475A-A16E-F10C30426E28@gmail.com>
Date: Mon, 9 Feb 2026 17:21:17 +0800
To: Postgres hackers <pgsql-hackers@lists.postgresql.org>
Archived-At: <https://www.postgresql.org/message-id/362EA9B3-589B-475A-A16E-F10C30426E28%40gmail.com>
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Hi,

I just noticed a bug in extension_file_exists():

```
bool
extension_file_exists(const char *extensionName)
{
	bool		result =3D false;
	List	   *locations;
	DIR		   *dir;
	struct dirent *de;

	locations =3D get_extension_control_directories();

	foreach_ptr(char, location, locations) // <=3D=3D Here type char =
is wrong
	{
		dir =3D AllocateDir(location);
```

get_extension_control_directories() returns a list of ExtensionLocation, =
but the loop iterates it as if it contained char *, which is incorrect. =
As a result, AllocateDir() and ReadDir() are called with the wrong type.

This bug is only triggered on an error path, when PostgreSQL is deciding =
whether to emit a hint. For example:
```
evantest=3D# create function f() returns int LANGUAGE plpython3u as =
$$return 1$$;
ERROR:  language "plpython3u" does not exist
```
No hint is printed.

With this patch applied:
```
evantest=3D# create function f() returns int LANGUAGE plpython3u as =
$$return 1$$;
ERROR:  language "plpython3u" does not exist
HINT:  Use CREATE EXTENSION to load the language into the database.
```
So the hint is shown as intended.

Attached is a patch fixing the iteration to use ExtensionLocation and =
location->loc consistently.

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/


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	filename=v1-0001-Fix-incorrect-iteration-type-in-extension_file_ex.patch
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