Linking to macOS frameworks

Sat May 22 22:29:48 UTC 2021

Ah, thanks for that.

My attempts were mostly based around loading the library in such a way that
either CLinker.systemLookup() or SymbolLookup.loaderLookup() could then
lookup the symbol for me. I had managed to get loaderLookup to work by way
of loading System.loadLibrary("osx");, which then let me dlopen libraries
whose symbols were available from loaderLookup but your method seems much
less hacky. Another attempt had me creating a custom SymbolLookup that
would call objc_getClass, but calling dlsym directly is a way more obvious
solution.

On Sat, May 22, 2021 at 4:00 PM Maurizio Cimadamore <
maurizio.cimadamore at oracle.com> wrote:

> I put together a quick Gist to show a possible approach:
>
> https://gist.github.com/mcimadamore/0883ea6f4836ae0c1d2a31c48197da1a
>
> This allows you to obtain a dlopen-based symbol lookup (see
> DlOpen::lookup). To open the library, the flag RTLD_LAZY is used. The
> provided scope is used to determine the library lifecycle - that is,
> when the scope is closed, the library will be unloaded.
>
> This is a fairly simple implementation, but it should allow you to "just
> use" dlopen/dlsym to load libraries and lookup sym.
>
> Maurizio
>
> On 22/05/2021 22:12, Maurizio Cimadamore wrote:
> > Hi,
> > in the new API, you could in principle use the linker API to create a
> > wrapper around dlopen/dlsym, and then wrap a SymbolLookup around that.
> >
> > You would have to be careful not to unload the library _while_ a
> > native function is being invoked (which is why we didn't provide such
> > an alternative out of the box - yet).
> >
> > We plan to have a more direct wrapper around dlopen in the future -
> > but we have to address this first:
> >
> > https://bugs.openjdk.java.net/browse/JDK-8267451
> >
> > to allow for safe unloading in the presence of multiple threads.
> >
> > Maurizio
> >
> > On 22/05/2021 20:02, Clayton Walker wrote:
> >> I've since updated to the most recent panama build, panama+3-167.
> >>
> >> Under Mojave I can load the IOKit library via
> >>
> System.load("/System/Library/Frameworks/IOKit.framework/Versions/A/IOKit");
> >>
> >> and then lookup the symbol "IORegistryGetRootEntry" via loaderLookup,
> >> however under Big Sur this code no longer works. While I can call
> >> dlopen manually under Big Sur, that doesn't make the symbols in the
> >> loaded library available to loaderLookup. This makes it frustrating
> >> trying to bind to native libraries on macOS.
> >>   I guess a workaround might be to create a dylib that links to a
> >> framework, then load that? But then you're back shipping native
> >> library shims.
> >>
> >> At least during testing, removing the file.exists() check from
> >> NativeLibaries.loadLibrary allowed the code to properly work under Big
> >> Sur.
> >>
> >> On Wed, May 19, 2021 at 3:12 PM Maurizio Cimadamore
> >> <maurizio.cimadamore at oracle.com> wrote:
> >>> I see.
> >>>
> >>> Obviously some kind of workaround is happening behind the scene when
> >>> dlopen is invoked with that library name, as a compatibility measure.
> >>>
> >>> If you load this:
> >>>
> >>> /usr/lib/libSystem.B.dylib
> >>>
> >>> Do you, by any change, get access to the symbols you want?
> >>>
> >>> Anyway - to your original question, LibraryLookup.ofPath works with a
> >>> library file in the file system. Here it seems a case where libraries
> >>> are not in the file system, but in some other cache, and dlopen has
> >>> been
> >>> instructed to "work" when asked with certain well-known names.
> >>>
> >>> In this case, if the above trick (libSystem) doesn't work, the only
> >>> thing left to you might well be calling dlopen directly.
> >>>
> >>> Maurizio
> >>>
> >>> On 19/05/2021 20:31, Clayton Walker wrote:
> >>>> Hi Maurizio,
> >>>>
> >>>> Yes, UserNotification is a library, but unfortunately
> >>>> UserNotification.dylib is no longer in that folder.
> >>>> Per this page
> >>>>
> https://urldefense.com/v3/__https://developer.apple.com/documentation/macos-release-notes/macos-big-sur-11_0_1-release-notes__;!!GqivPVa7Brio!PxJkXokERrp3NAcaRqK7q1eIHPqhs9AWyxmbu4_AfBKvGVbf2OcqtR2HUvwImxChbwHDpmE$
> >>>> ,
> >>>> Apple's release notes state
> >>>> `copies of dynamic libraries are no longer present on the filesystem`.
> >>>> So while previously they did exist on the filesystem, now they're not.
> >>>> dlopen still handles the path on macOS Big Sur,
> >>>>
> dlopen("/System/Library/Frameworks/UserNotifications.framework/Versions/Current/UserNotifications");
>
> >>>>
> >>>> works.
> >>>>
> >>>>
> >>>> On Wed, May 19, 2021 at 11:03 AM Maurizio Cimadamore
> >>>> <maurizio.cimadamore at oracle.com> wrote:
> >>>>> Hi Clayton,
> >>>>> Is UserNotification a library? E.g. is there a file
> >>>>> UserNotification.dylib in that folder?
> >>>>>
> >>>>> If so, just use "Library.ofPath" and include the suffix - as that
> >>>>> method
> >>>>> wants the library absolute path.
> >>>>>
> >>>>> Maurizio
> >>>>>
> >>>>> On 19/05/2021 17:46, Clayton Walker wrote:
> >>>>>> Hello,
> >>>>>>
> >>>>>> I'm working on a project that would let you call objective-c
> >>>>>> functions from
> >>>>>> java, without first needing to wrap the api in a shared library.
> >>>>>> While this
> >>>>>> works for symbols that are already available
> >>>>>> (i.e.LibraryLookup.ofDefault().lookup("objc_getClass")), it
> >>>>>> doesn't work
> >>>>>> for symbols that are in another framework.
> >>>>>>
> >>>>>> For example, I would like to be able to write something like this:
> >>>>>>
> LibraryLookup.ofLibrary("/System/Library/Frameworks/UserNotifications.framework/Versions/Current/UserNotifications");
>
> >>>>>>
> >>>>>> // or
> >>>>>>
> LibraryLookup.ofPath(Path.of("/System/Library/Frameworks/UserNotifications.framework/Versions/Current/UserNotifications"));
>
> >>>>>>
> >>>>>> however this currently doesn't work. The first call throws with
> >>>>>> "Directory
> >>>>>> separator should not appear in library name", second one throws with
> >>>>>> "Library not found".
> >>>>>>
> >>>>>> I've been able to work around this by using dlopen
> >>>>>> MemoryAddress l1;
> >>>>>> try (var c =
> >>>>>>
> CLinker.toCString("/System/Library/Frameworks/UserNotifications.framework/Versions/Current/UserNotifications"))
>
> >>>>>>
> >>>>>> {
> >>>>>>        l1 = (MemoryAddress) dlopen.invokeExact(c.address(), 1);
> >>>>>> }
> >>>>>> but this seems rather strange. It looks like LibraryLookup.ofPath
> >>>>>> requires
> >>>>>> the path to exist, whereas in Big Sur the files no longer exist (via
> >>>>>>
> https://urldefense.com/v3/__https://developer.apple.com/forums/thread/657267__;!!GqivPVa7Brio!PxJkXokERrp3NAcaRqK7q1eIHPqhs9AWyxmbu4_AfBKvGVbf2OcqtR2HUvwImxChS2opDZY$
> >>>>>> ).
>