[foreign] does static forwarder generation has to depend on -l presence?

[Sundararajan Athijegannathan]

Maurizio convinced me offline ;) I'll do change static forwarder 
generation (generate regardless of -l)

Thanks,
-Sundar

On 02/05/19, 6:38 PM, Jorn Vernee wrote:
> Thinking some more about this; Note that the presence of static 
> forwarders doesn't change the use of the default library. Currently, 
> if -l is not specified, the default library will still be used by the 
> binder for the header class if no libraries attribute is specified in 
> NativeHeader.
>
> Alternatively, we could also do away with the native RTLD_DEFAULT and 
> EnumProcessModules lookup and instead implement the default library 
> behaviour on the Java side as a SymbolLookup instance that iterates a 
> set of libraries e.g. taken from LD_LIBRARY_PATH, and perhaps others, 
> and tries the symbol lookup in each one. This ensures the behaviour is 
> more consistent across platforms.
>
> Jorn
>
> Jorn Vernee schreef op 2019-05-02 14:18:
>> Yes, we have to walk all modules loaded by the process. But, I imagine
>> the internal implementation of RTLD_DEFAULT is pretty similar?
>>
>> The LD_LIBRARY_PATH behavior doesn't apply to Windows either, since
>> it's an implementation detail of dlsym, so using the default library
>> really only gives someone access to libraries loaded previously by
>> some other mechanism, e.g. System.loadLibrary.
>>
>> I think it's not needed to worry about performance at this point. If
>> better performance is needed the -l option can be used as well.
>>
>> Jorn
>>
>> Sundararajan Athijegannathan schreef op 2019-05-02 13:53:
>>> Default library on Windows is a bit costly, right? i.e., we have to
>>> walk all loaded modules? The API used is meant for debug use if I
>>> recall.
>>>
>>> -Sundar
>>>
>>> On 02/05/19, 5:00 PM, Jorn Vernee wrote:
>>>> I think there was some caution when they were added, but over time 
>>>> we have started relying on static forwarders more and more. I think 
>>>> it makes sense to always generate the static forwarders. The 
>>>> generation can always be turned off again using the command line 
>>>> option if needed.
>>>>
>>>> Jorn
>>>>
>>>> Maurizio Cimadamore schreef op 2019-05-02 12:50:
>>>>> Hi,
>>>>> as I was playing with some stdlib examples, I noted that jextract was
>>>>> not generating any static forwarder for me. I was then reminded that
>>>>> static forwarders are only emitted if some library is passed via the
>>>>> -l option.
>>>>>
>>>>> Is this too strict? After all, we have a 'default' Library that we 
>>>>> can
>>>>> use as resolution context, which will pick up anything loaded by the
>>>>> VM (which also includes things in paths specified in sys variables
>>>>> like LD_LIBRARY_PATH). So, would it make sense to relax static
>>>>> forwarder generation so that, in the absence of -l, it will just use
>>>>> the default library?
>>>>>
>>>>> That would improve usability in certain cases.
>>>>>
>>>>> Maurizio