<Swing Dev> RFR(S): 8156020: 8145547 breaks AIX and and uses RTLD_NOLOAD incorrectly

[Semyon Sadetsky]

Hi Volker,

I did not answer you because I was on leave. Thank you for your 
attention to the problem. It looks like that you found the issue we 
could not find.
For some reason I thought that RTLD_NOLOAD and RTLD_LAZY flags are 
mutually excluded, and unfortunately the reviewers did not notice that 
even when I pointed the  problem with dl_open() out in our internal 
discussions.
We knew that the lib detection doesn't work but since we were a bit 
under pressure I've pushed the JEP as it is and filed the 8154994 for 
further investigation which can be closed after your fix push.
The procfs solution (V6) was a work around attempt which has never been 
approved and couldn't be pushed, so the V5 is pushed correctly.
On Solaris the GTK3 library is not supported, thus it should not be a 
problem if isLoadedLib() will return false always there.
The target platforms was Linux and OEL on which GTK2/GTK3 
incompatibility is an issue. AFAIK AIX and BSD are not supported by 
JDK9, but I have no doubts that a solution that supports most Unix 
flavors is preferable, especially since it is not very difficult.

--Semyon


On 5/4/2016 9:32 PM, Volker Simonis wrote:
> Hi,
>
> can somebody please review this small change which fixes the AIX build
> after change 8145547, but also fixes an incorrect usage pattern of
> RTLD_NOLOAD in 8145547:
>
> http://cr.openjdk.java.net/~simonis/webrevs/2016/8156020/
> https://bugs.openjdk.java.net/browse/JDK-8156020
>
> Here are the details from the bug report:
>
> Change 8145547 uses the RTLD_NOLOAD flag when calling dlopen to probe
> the availability of the GTK libraries.
>
> But unfortunately RTLD_NOLOAD is not Posix and for example not
> available on AIX and BSD.
>
> I also found out, that the implementation of 8145547 contains a bug.
> It uses RTLD_NOLOAD in an incorrect way. The man page for dlopen
> clearly states that one of the two flags RTLD_LAZY or RTLD_NOW has to
> be included in the flags. But the current implementation uses
> RTLD_NOLOAD as single flag. Therefor the call to dlopen() currently
> always returns NULL, no difference if the corresponding library has
> been loaded already or not.
>
> The bug report also contains a small C program which can be used to
> reproduce the problem.
>
> The fix is to only use RTLD_NOLOAD if it is defined. The change
> removes the 'flags' argument from the various check() functions and
> replaces it with a boolean 'load' argument. It indicates if the check
> functions should just look for a previously loaded version of the GTK
> libraries (i.e. if 'load' == false) or if it should additionally try
> to load the libraries if that hasn't been done before (i.e. if 'load'
> == true).
>
> I hope I haven't changed the previous program semantics with my
> change. At least I couldn't see any difference :)
>
> I've built and smoke tested on Linux/Solaris and AIX with various
> combinations for jdk.gtk.version,
> -Dswing.defaultlaf=com.sun.java.swing.plaf.gtk.GTKLookAndFeel and
> FileDialog implementations.
>
> I'd like to push this directly to jdk9-dev to fix the AIX build as
> fast as possible. Would that be OK?
>
> Thank you and best regards,
> Volker