RFR: 8166189: Fix for Bug 8165524 breaks AIX build

[Kumar Srinivasan]

Hello Thomas, Volker,

>
> Hi Kumar,
>
>
>     On 9/16/2016 10:34 AM, Volker Simonis wrote:
>
>         Hi Christoph,
>
>         I think your change is fine as a quick-fix to fix the build. But
>         you're completely right that this should be reworked in the
>         long term.
>         I hate to see that we now have the third version of these
>         routines in
>         the OpenJDK. Unfortunately a clean solution is not trivial.
>
>         libjli is not linked against libjvm because libjli is actually
>         used to
>         load libjvm. So we can not put the dladdr routines for AIX
>         there. But
>         I think we should at least consolidate the two versions which
>         will be
>         in the class library after your change. Initially I
>         intentionally put
>         porting_aix.{c,h} into jdk/aix/porting with the intent to make it
>         available to ALL jdk native libraries.
>
>         Unfortunately, with the source code reorganization due to the
>         modular
>         changes, the common, top-level aix repository had to go away
>         and the
>         code was moved to
>         src/java.desktop/aix/native/libawt/porting_aix.c.
>         With the reorganized, modularized source code layout and build
>         system
>         it is not possible to share code between modules. We somehow
>         have to
>         fix this although I currently don't know how. IF somebody has
>         an idea,
>         please let me know :)
>
>
>     Why doesn't AIX support a Standard C API that most other
>     *nix based OS'es support ?
>
>
> dladdr() is not Posix, hence it should not be used in code that wants 
> to be portable across Unix systems. Afaik dladdr() is a propietary 
> Solaris API that was adapted by the glibc and slowly spread over to 
> some other Unices, but by no means all of them.
> dladdr makes a number of assumptions about the architecture: e.g. that 
> a C function pointer points into the text segment of the binary 
> instead of e.g. a PLT, or that a loaded binary is placed continuously 
> in memory (we only have one dli_fbase in DL_info). So imho  it makes 
> sense to not make this a standard Posix API.
>
> We (SAP) implemented dladdr atop of loadquery(), and this kind of 
> works, although we had to add some hacks to handle both real code 
> addresses and C function pointers. So the code is there, it is "just" 
> a question of where to place it.

I understand your desire to keep AIX pristine and clean, similarly,
we should also keep  OpenJDK sources clean, having 3 identical
dladdr implementation, spread across the OpenJDK does not
bode well.

So, is it possible to park the sources in hotspot repo, and create a
shared shared object, that can be suitably linked to the launchers,
awt and hotspot to this library/object ?

Thanks
Kumar



> Kind Regards, Thomas
>
>     Thanks
>
>     Kumar
>
>
>
>         Regarding your change:
>
>         - can you please move
>
>         +#if defined(_AIX)
>         +#include "java_md_aix.h"
>         +#endif
>         +
>
>         from java_md_common.c to the end of
>         java.base/unix/native/libjli/java_md.h. It will then be
>         automatically
>         included into java_md_common.c trough java.h which includes
>         java_md.h
>
>         Also, this version of dladdr is inherently not thread safe. I
>         don't
>         think that's a problem here, but it would be nice if you could
>         quickly
>         check if that's indeed true.
>
>         Besides that, looks good.
>
>         Thanks for fixing,
>         Volker
>
>
>
>
>         On Fri, Sep 16, 2016 at 11:58 AM, Langer, Christoph
>         <christoph.langer at sap.com <mailto:christoph.langer at sap.com>>
>         wrote:
>
>             Hi,
>
>             the fix for
>             https://bugs.openjdk.java.net/browse/JDK-8165524
>             <https://bugs.openjdk.java.net/browse/JDK-8165524> breaks
>             the AIX build as function dladdr is not available on AIX.
>
>             There already exist ports of that API in hotspot and awt.
>             With the proposed change I duplicate the awt port to
>             libjli. This is maybe only a quick fix - eventually we
>             should think about consolidating and using the hotspot
>             port in all places by exporting it from libjvm.so for AIX.
>
>             Bug: https://bugs.openjdk.java.net/browse/JDK-8166189
>             <https://bugs.openjdk.java.net/browse/JDK-8166189>
>             Webrev:
>             http://cr.openjdk.java.net/~clanger/webrevs/8166189.0/
>             <http://cr.openjdk.java.net/%7Eclanger/webrevs/8166189.0/>
>
>             Thanks
>             Christoph
>
>
>                 -----Original Message-----
>                 From: core-libs-dev
>                 [mailto:core-libs-dev-bounces at openjdk.java.net
>                 <mailto:core-libs-dev-bounces at openjdk.java.net>] On Behalf
>                 Of Kumar Srinivasan
>                 Sent: Montag, 12. September 2016 22:57
>                 To: core-libs-dev <core-libs-dev at openjdk.java.net
>                 <mailto:core-libs-dev at openjdk.java.net>>; Mandy Chung
>                 <mandy.chung at oracle.com
>                 <mailto:mandy.chung at oracle.com>>; Chris Bensen
>                 <chris.bensen at oracle.com <mailto:chris.bensen at oracle.com>>
>                 Subject: RFR: 8165524: Better detect JRE that Linux
>                 JLI will be using
>
>                 Hello,
>
>                 I am sponsoring this changeset for Chris Bensen of the
>                 java packager
>                 team, please review  fix for the launcher to better
>                 locate java.home.
>
>                 http://cr.openjdk.java.net/~ksrini/8165524/
>                 <http://cr.openjdk.java.net/%7Eksrini/8165524/>
>
>                 Thanks
>                 Kumar
>
>
>