On Thu, 13 May 2021 20:46:28 GMT, Phil Race <p...@openjdk.org> wrote:
>> Tejpal Rebari has updated the pull request incrementally with one additional
>> commit since the last revision:
>>
>> code cleanup
>
> 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).
-------------
PR: https://git.openjdk.java.net/jdk/pull/3407
