Integrated: 8323664: java/awt/font/JNICheck/FreeTypeScalerJNICheck.java still fails with JNI warning on some Windows configurations

[Christoph Langer]

On Fri, 12 Jan 2024 17:47:23 GMT, Christoph Langer <clanger at openjdk.org> wrote:

> This picks up fixing the issue of [JDK-8276809](https://bugs.openjdk.org/browse/JDK-8276809) again. A fix had been integrated with #17224 but @prrace had concerns and so it was backed out.
> 
> I have now spent quite some thoughts into the problem and end up with the [initial commit](https://github.com/openjdk/jdk/pull/6306/commits/5d18a76cb967e9ede6394cbd6c28bb61facf785c) of #6306 as the most elegant and least intrusive solution.
> 
> Why is this?
> 
> The JNI warning we observe in the test is:
> `[WARNING in native method: JNI call made without checking exceptions when required to from CallStaticVoidMethodV
> 	at sun.awt.Win32GraphicsEnvironment.initDisplay(java.desktop at 22.0.1-internal/Native Method)
> 	at sun.awt.Win32GraphicsEnvironment.initDisplayWrapper(java.desktop at 22.0.1-internal/Win32GraphicsEnvironment.java:95)
> 	at sun.awt.Win32GraphicsEnvironment.<clinit>(java.desktop at 22.0.1-internal/Win32GraphicsEnvironment.java:63)
>         ...
>         at FreeTypeScalerJNICheck.runTest(FreeTypeScalerJNICheck.java:53)
> 	at FreeTypeScalerJNICheck.main(FreeTypeScalerJNICheck.java:44)`
> 
> This happens because obviously the test FreeTypeScalerJNICheck runs with `-Xcheck:jni` and in the scenario where we're observing the warning, a missing exception check for the JNI call to `sun.awt.Win32GraphicsEnvironment::dwmCompositionChanged` at awt_Win32GraphicsEnv.cpp#L129
> https://github.com/openjdk/jdk/blob/c5e72450966ad50d57a8d22e9d634bfcb319aee9/src/java.desktop/windows/native/libawt/windows/awt_Win32GraphicsEnv.cpp#L129 is airing up. Omitting the exception check would not be a problem if it could be guaranteed that after this call no other JNI->Java call was being made. But seemingly in this very particular configuration on some of our Windows servers, there must be JNI->Java calls that follow the call to `sun.awt.Win32GraphicsEnvironment::dwmCompositionChanged`, likely from the subsequent call to [initScreens](https://github.com/openjdk/jdk/blob/c5e72450966ad50d57a8d22e9d634bfcb319aee9/src/java.desktop/windows/native/libawt/windows/awt_Win32GraphicsEnv.cpp#L149) in `sun.awt.Win32GraphicsEnvironment::initDisplay`. https://github.com/openjdk/jdk/blob/8b6293f6bfb7b7628c6604e6c44401fc96d85cf4/src/java.desktop/windows/native/libawt/windows/awt_Win32GraphicsEnv.cpp#L141 Maybe the usual control flow would call the wrapping native method `DWMIsCompositi
 onEnabled()` from somewhere else initially such that the initialization of `Win32GraphicsEnvironment` would not go through `initScreens` or similar.
> ...

This pull request has now been integrated.

Changeset: 99c9ae12
Author:    Christoph Langer <clanger at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/99c9ae127c0a3b8c4fc6ede87079ff7c693a2905
Stats:     21 lines in 2 files changed: 5 ins; 5 del; 11 mod

8323664: java/awt/font/JNICheck/FreeTypeScalerJNICheck.java still fails with JNI warning on some Windows configurations

Reviewed-by: prr, mbaesken, aivanov

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PR: https://git.openjdk.org/jdk/pull/17404