RFR: 8353632: [Linux] Undefined reference to PlatformSupport::OBSERVED_SETTINGS with C++14

[John Neffenger]

On Thu, 10 Apr 2025 16:11:07 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

> Fixes a link error that occurs when using C++14 to compile and link JavaFX on Linux.
> 
> 
> in function `PlatformSupport::PlatformSupport(JNIEnv_*, _jobject*)':
> PlatformSupport.cpp:90: undefined reference to `PlatformSupport::OBSERVED_SETTINGS'
> 
> 
> The solution, proposed by @johanvos, is to define `PlatformSupport::OBSERVED_SETTINGS` in `PlatformSupport.cpp`.
> 
> I have tested this using gcc 13.2 and 14.2 using C++17 and it builds and runs as expected. Johan has already tested a variant of this on C++14, but I will wait for his explicit review.

Just a note in case anyone else encounters a related runtime error ...

When I built JavaFX using either gcc version 7.4.0 on Ubuntu 18.04 LTS or gcc version 9.3.0 on Ubuntu 20.04 LTS, I got the following error at runtime:


Exception in thread "main" java.lang.reflect.InvocationTargetException
    Caused by: java.lang.UnsatisfiedLinkError: libglassgtk3.so:
    undefined symbol: _ZN15PlatformSupport17OBSERVED_SETTINGSE


The runtime error did not occur after I upgraded the build system to gcc version 11.2.0 on Ubuntu 22.04 LTS, so I didn't debug it any further.

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PR Comment: https://git.openjdk.org/jfx/pull/1768#issuecomment-2798225280