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

[Jorn Vernee]

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