Linking against c++ standard library?

[Christoph Läubrich]

 > That said, you might try calling dlopen directly using the linker, and
 > passing the required flags.

I'll give it a try!

 > Have you tried using LD_PRELOAD?

LD_PRELOAD seems to do the trick, so now one just needs to perform 
similar from Panama directly :-D


Am 03.08.23 um 17:21 schrieb Maurizio Cimadamore:
> Unfortunately, the JDK only loads with RTLD_LAZY, not GLOBAL.
> 
> That said, you might try calling dlopen directly using the linker, and 
> passing the required flags.
> 
> Have you tried using LD_PRELOAD?
> 
> Maurizio
> 
> On 03/08/2023 16:16, Christoph Läubrich wrote:
>> Hi Maurizio
>>
>> thanks for your fast replay, in the stackoverflow there is a hint that 
>> says:
>>
>> > If you load libmono dynamically at runtime
>> (I think thats my case)
>>
>> > you'll have to load in libstdc++ first, using something like this:
>> > void * cxxlib = dlopen("libstdc++.so.6", RTLD_LAZY | RTLD_GLOBAL);
>>
>> (that's what I tried with System.load)
>>
>> BUT:
>> > Key thing here is the RTLD_GLOBAL flag, which will add all symbols 
>> to the global table, so they can be found when you're trying to load 
>> libmono.
>>
>> So it seems this RTLD_GLOBAL flag is somehow the missing magic (and 
>> System.load probabbly is not using that), can I somehow issue an 
>> dlopen with panama that includes this flag?
>>
>> Also I can recompile the lib but have no clue what would be the 
>> "right" way to add the dependency and of course then it only works 
>> with custom compiled version so I hopped I can somehow trick the JVM 
>> here :-)
>>
>> best
>> Christoph
>>
>>
>> Am 03.08.23 um 17:03 schrieb Maurizio Cimadamore:
>>> Hi,
>>> not an expert on the topic, but also found this:
>>>
>>> https://stackoverflow.com/questions/67910722/how-to-deal-with-undefined-symbols-when-loading-mono-libraries-in-linux
>>>
>>> It seems like libmono doesn't come with the right dynamic 
>>> dependencies on it? (so library loading would fail).
>>>
>>> I don't think this is something you can fix on the Java side. You 
>>> need a library that has the right set of dependencies.
>>>
>>> Maurizio
>>>
>>> On 03/08/2023 15:53, Christoph Läubrich wrote:
>>>> I used an older lib of "mono" [1] (v5) with panama without a problem 
>>>> and everything worked out quite well but with v6 of the lib I can't 
>>>> load it anymore because it fails [2] with "undefined symbol: 
>>>> _ZTIPi", the maintainer of the lib responded that
>>>>
>>>> "though on modern Mono, you need to link against a C++ standard 
>>>> library"
>>>>
>>>> so my first guess was to add System.load("stdc++") but this seem not 
>>>> working (at least it results in the same error message).
>>>>
>>>> So I wonder if there is anything special I can do to tell panama to 
>>>> link/load a c++ standard library?
>>>>
>>>>
>>>>
>>>> [1] https://www.mono-project.com/
>>>> [2] https://github.com/mono/mono/issues/21676