Questions about JEP442 at https://openjdk.org/jeps/442

[Cheng Jin]

Hi there,

I feel confused with the following descriptions in JEP442 at https://openjdk.org/jeps/442:
Provided a linker option to optimize calls to functions that are short-lived and will not upcall to Java (e.g., clock_gettime);

Can anybody explain what the linker option is intended for (assuming it is used in upcall?) and how it works in terms of the optimization in there?


Another question is about the fallback linker: Provided a fallback native linker implementation, based on libffi

It seems to me t that it is never used unless the current platform has no support on the foreign linker as indicated in code at java.base/share/classes/jdk/internal/foreign/CABI.java:

       if (ForeignLinkerSupport.isSupported()) {
       ...
       } else if (FallbackLinker.isSupported()) {
            return FALLBACK; // fallback linker
       }

If so, what is the background of introducing this kind of linker? and where can it be used?

Best Regards
Cheng Jin
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