On Thu, 13 May 2021 21:37:18 GMT, Kevin Rushforth <[email protected]> wrote:
>> src/java.desktop/macosx/native/libawt_lwawt/awt/AWTWindow.m line 1106:
>>
>>> 1104: {
>>> 1105: JNI_COCOA_ENTER(env);
>>> 1106: if (@available(macOS 10.12, *)) {
>>
>> @kevinrushforth said that since we set MIN_SDK (not sure of the exact
>> variable name) to 10.12, that this is compiled down to a no-op .. which
>> means it is useless and doesn't protect you from making the call on 10.11
>> So you might as well remove it. It won't prevent the crash that will happen
>> on 10.11.
>> @mrserb also pointed out people might then copy this pattern not realising
>> it does not work, and there's a better way ... apparently ...
>
> Right. @johanvos discovered this fun fact about `@available` when he got a
> crash report from a user. He filed
> [JDK-8266743](https://bugs.openjdk.java.net/browse/JDK-8266743), which
> describes this problem.
>
> The setting of minimum version of macOS is controlled by the
> `-mmacosx-version-min` compile and link flag. The minimum version is defined
> in
> [make/autoconf/flags.m4](https://github.com/openjdk/jdk/blob/master/make/autoconf/flags.m4#L136)
> and used in
> [make/autoconf/flags-cflags.m4](https://github.com/openjdk/jdk/blob/master/make/autoconf/flags-cflags.m4#L555).
>
> One thing I don't know (and can't try, since I don't have access to a macOS
> system that old) is whether the JDK will fail somewhere else anyway (e.g., if
> they check for a minimum OS at start up). So this might be a moot point, but
> as it stands, I think @mrserb is right that we should avoid this pattern. I
> would probably just remove it, but you could decide to use something like
> `respondsToSelector` (which is what I think Sergey was suggesting).
Since OpenJFX does not have its own launcher and IIRC JDK only recently (JDK 17
b08 https://bugs.openjdk.java.net/browse/JDK-8260518 ) set the minimum to 10.12
it is possible that the submitter of the FX crash was using A JDK prior to
that, in which case I am sure the Java Launcher would start up fine and you'd
crash only when calling this code. So also I think very aguably *library* code
has another reason to avoid this pattern.
And verifying what happens on 10.11 might be best done with a launcher from JDK
17 b07 or later .. also @kevinrushforth you might want to add some of these
thoughts to the FX bug.
-------------
PR: https://git.openjdk.java.net/jdk/pull/3407
