[External] : Is libsyslookup.so needed for FFM on Linux?

[suenaga]

Hi all,

I found libsyslookup.so in lib directory in JDK, and it seems to be used 
in `SystemLookup` in FFM to find symbols from the system. But I wonder 
why SystemLookup depends on libsyslookup on Linux. I think it is not 
needed on Linux with some changes.

I understand syslookup.dll is needed for Windows because some functions 
might not be lookup'ed. OTOH on Linux, `dlsym` can lookup symbols from 
library dependencies. In `SystemLookup`, handle of libsyslookup would be 
passed to `dlsym` eventually, but I think it is better to pass 
`RTLD_DEFAULT` in this case. I know it works when the handle of 
libsyslookup is passed, but `RTLD_DEFAULT` is better because Javadoc of 
`Linker::defaultLookup` says it returns a set of commonly used 
libraries. I guess the reson of use libsyslookup is to use 
`NativeLibraryImpl`.

I think we can fix not to use libsyslookup like [1]. It works on Linux 
(including static image of course). If it does not have a problem, I 
want to create JBS issue and PR for this. Do you have any comments?

In addition, I guess we can apply this change to all of POSIX platforms 
because `dlsym` is defined in POSIX, but I'm not sure we can do 
(especially AIX - it has own syslookup.c in JDK source tree).


Thanks,

Yasumasa


[1] 
https://github.com/YaSuenag/jdk/commit/b125cc164d60ac14316549e59d18544d75f6fcb2