Re: Fix a bug in extension_file_exists()

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