RFR: JDK-8320830: [AIX] Dont mix os::dll_load() with direct dlclose() calls [v2]

[Joachim Kern]

On Thu, 30 Nov 2023 08:47:16 GMT, Joachim Kern <jkern at openjdk.org> wrote:

>> We should not mix os::dll_load() with dlclose(), but should call os::dll_unload(). At the moment this is benign, but this prevents certain type of platforms specific workarounds inside os::dll_load() and is a prerequisite for these upcoming changes. 
>> 
>> There are two places I see where this happens, both are AIX specific:
>> 
>> 
>> os/aix/libodm_aix.cpp
>> 51: dlclose(_libhandle);
>> 58: if (_libhandle) { dlclose(_libhandle); }
>> 
>> os/aix/libperfstat_aix.cpp
>> 117: dlclose(g_libhandle);
>
> Joachim Kern has updated the pull request incrementally with one additional commit since the last revision:
> 
>   replaced local scope by class scope

src/hotspot/os/aix/libodm_aix.cpp line 39:

> 37:   char ebuf[512];
> 38:   _libhandle = os::dll_load(libodmname, ebuf, sizeof(ebuf));
> 39: 

_libhandle is a class member. Here it was accidentally defined with function local scope, so the class member _libhandle stayed uninitialized. As a result the dll_unload() in the destructor worked with a garbage value of the class member. This change fixes this problem.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16846#discussion_r1410341167