RFR: JDK-8320890: [AIX] Find a better way to mimic dl handle equality [v5]

[Joachim Kern]

On Mon, 18 Dec 2023 10:16:07 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>> Joachim Kern has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - trailing whitespace
>>  - Following most of Thomas proposals
>
> src/hotspot/os/aix/porting_aix.cpp line 1005:
> 
>> 1003:     // LIBPATH or LD_LIBRARY_PATH and second with burned in libpath.
>> 1004:     // No check against current working directory
>> 1005:     Libpath.print("%s:%s", env, rtv_linkedin_libpath());
> 
> Are you sure libpath env var has precedence over the baked-in libpath?

Yes, that was the outcome of my experiments, although the IBM docu says the oposite:
_"Specifies that the library path used at process exec time should be prepended to any library path specified in the load call (either as an argument or environment variable). It is recommended that this flag be specified in all calls to the load subroutine."_ 

My experiment showed: LIBPATH=libpath; baked-in-libpath=baked-in-libpath;
mylib.so is in both paths. After dlopen(mylib.so) a map call shows the library was loaded from libpath.
Then I remove the LIBPATH envvar and repeat. Now after dlopen(mylib.so) a map call shows the library was loaded from baked-in-libpath.
So the LIBPATH envvar has precedence over the baked-in-libpath.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16920#discussion_r1429919510