RFR: 8268129: LibraryLookup::ofDefault leaks symbols from loaded libraries

[Jorn Vernee]

On Wed, 2 Jun 2021 17:19:06 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

> This patch overhauls the library loading mechanism used by the Foreign Linker API. We realized that, while handy, the *default* lookup abstraction (`LibraryLookup::ofDefault`) was behaving inconsistentlt across platforms.
> 
> This patch replaces `LibraryLookup` with a simpler `SymbolLookup` abstraction, a functional interface. Crucially, `SymbolLookup` does not concern with library loading, only symbol lookup. For this reason, two factories are added:
> 
> * `SymbolLookup::loaderLookup` - which obtains a lookup that can be used to lookup symbols in libraries loaded by current loader
> * `CLinker::systemLookup` - a more stable replacement for the *default* lookup, which looks for symbols in libc.so (or its equivalent in other platforms). The contents of this lookup are unspecified.
> 
> Both factories are *restricted*, so they can only be called when `--enable-native-access` is set.

LGTM, minor nit inline

test/micro/org/openjdk/bench/jdk/incubator/foreign/points/support/PanamaPoint.java line 62:

> 60:         );
> 61:         MH_distance_ptrs = abi.downcallHandle(
> 62:                 lookup.lookup("distance_ptrs").get(),

Spurious white space
Suggestion:

            lookup.lookup("distance_ptrs").get(),

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Marked as reviewed by jvernee (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/4316