RFR: 8365609: Fix several potential NULL native pointer dereferences in the desktop module [v2]

[Artem Semenov]

On Fri, 22 Aug 2025 04:34:00 GMT, Phil Race <prr at openjdk.org> wrote:

>>> I don't know why we don't treat failing to find this symbol as a fatal error like we do for others such as this first one.
>> 
>> It looks like the `glib_check_version` was added but never used. The first instance of its use appears to be the added check for the methods used for Screencast. And it was overlooked that the `fp_glib_check_version` can be `null`.
>> 
>> The `glib_check_version` is [available since 2.6](https://docs.gtk.org/glib/func.check_version.html), and the 2.6.0 [was released in 2004](https://mail.gnome.org/archives/gnome-announce-list/2004-December/msg00036.html), so I guess we can safely replace the `dlsym` with the `dl_symbol`.
>> This will be better than remembering to protect it with a null check if we decide to use `glib_check_version` later somewhere else.
>> 
>> 
>> 
>> -        fp_glib_check_version = dlsym(gtk3_libhandle, "glib_check_version");
>> -        if (!fp_glib_check_version) {
>> -            dlerror();
>> -        }
>> +        fp_glib_check_version = dl_symbol("glib_check_version");
>
> So that would be the proper fix here, not the proposed one.

> > I don't know why we don't treat failing to find this symbol as a fatal error like we do for others such as this first one.
> 
> It looks like the `glib_check_version` was added but never used. The first instance of its use appears to be the added check for the methods used for Screencast. And it was overlooked that the `fp_glib_check_version` can be `null`.
> 
> The `glib_check_version` is [available since 2.6](https://docs.gtk.org/glib/func.check_version.html), and the 2.6.0 [was released in 2004](https://mail.gnome.org/archives/gnome-announce-list/2004-December/msg00036.html), so I guess we can safely replace the `dlsym` with the `dl_symbol`. This will be better than remembering to protect it with a null check if we decide to use `glib_check_version` later somewhere else.
> 
> ```diff
> -        fp_glib_check_version = dlsym(gtk3_libhandle, "glib_check_version");
> -        if (!fp_glib_check_version) {
> -            dlerror();
> -        }
> +        fp_glib_check_version = dl_symbol("glib_check_version");
> ```

done

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PR Review Comment: https://git.openjdk.org/jdk/pull/26799#discussion_r2300094456