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From: Chao Li <[email protected]>
To: Heikki Linnakangas <[email protected]>
Cc: Postgres hackers <[email protected]>
Subject: Re: Fix a bug in extension_file_exists()
Date: Tue, 10 Feb 2026 08:50:10 +0800
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<[email protected]>



> On Feb 9, 2026, at 18:02, Heikki Linnakangas <[email protected]> wrote:
> 
> On 09/02/2026 11:21, Chao Li wrote:
>> I just noticed a bug in extension_file_exists():
>> ```
>> bool
>> extension_file_exists(const char *extensionName)
>> {
>> bool result = false;
>> List   *locations;
>> DIR   *dir;
>> struct dirent *de;
>> locations = get_extension_control_directories();
>> foreach_ptr(char, location, locations) // <== Here type char is wrong
>> {
>> dir = 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=# 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=# 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.
> 
> Yep, good catch. This went wrong in commit f3c9e341cd, which changed the type of objects in the list from "char *" to "ExtensionLocation *". So this is master only, stable branches are not affected.
> 
> I will push the fix shortly, thanks!
> 
> - Heikki
> 

Thanks for pushing.

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

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