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From: Matheus Alcantara <[email protected]>
To: Heikki Linnakangas <[email protected]>
To: Chao Li <[email protected]>
To: Postgres hackers <[email protected]>
Subject: Re: Fix a bug in extension_file_exists()
Date: Mon, 9 Feb 2026 10:19:20 -0300
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<[email protected]>

On 09/02/26 07:02, Heikki Linnakangas 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!
>
Sorry, I miss this change.

Thanks for the patch Chao and Heikki for committing.


-- 
Matheus Alcantara
EDB: https://www.enterprisedb.com

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