I wanted to know if the moduleName was cached somewhere or recomputed at each function call...
It seems to be recomputed.
We could have a different scheme:
moduleName is cached in a class inst var of FFILibrary.
FFILibrary is then added to startup list and moduleName is reset when resuming on a different platform.
instance side moduleName calls class side moduleName.
Or moduleName becomes an inst var, set during uniqueInstance construction, and uniqueInstance is nilled out when resuming.
What do you think?
Do you mean when using a symbol/string as module like...?
ioFindSurface: id dispatch: dispPtr handle: handlePtr
self ffiCall: #( bool ioFindSurface(int id, void * dispPtr, int *handlePtr) ) module: #SurfacePlugin
As I see it, there are two (basic) schemas to do FFI calls using UFFI
- using a library object. Library objects are actual singletons stored in class instance variables
FFILibrary class >> uniqueInstance
self = FFILibrary
ifTrue: [ self error: 'I''m an abstract class, use one of my children.' ].
^ uniqueInstance ifNil: [ uniqueInstance := super new ]
- using a symbol/string, then a module is created dynamically
String >> asFFILibrary
^ FFIUnknownLibrary name: self
But, but :) the thing is that ffi calls in UFFI are lazily compiled using bytecode transformations and there (if I'm not mistaken) the library instances created are cached on the callout object stored as a literal in the method.
So there is a cache, but per ffi call. And then, at shutdown, all the generated methods (bound to a specific external function) are wiped out.
All this process is of course perfectible and probably a "coup de" profiling could be nice ^^.
Well, when I designed the FFILibrary I first thought: let’s the user decide if they want to cache or not (because most of the time is not worthy, since as Guille says it is cached on each method and usually is straightforward)
Then I thought that maybe I should add a generic cache mechanism, for those cases where you need to perform complicated locates. But I did not had the time to do it.
So, I would say: yes, it would be good to have a cache mechanism, but most of the time is not needed (and caches are dangerous things so better to reduce their usage at max).
If someone wants to implement that for their library, they can.
If someone wants to implement a generic mechanism and contribute it, it would be also welcomed :)
Do you know if this points is documented in the FFILibrary class comments?
Can you add a bug entry so that we do not forget?
In reply to this post by EstebanLM
On Mon, 14 Jan 2019 at 17:12, Esteban Lorenzano <[hidden email]> wrote:
One thing that was get easily confusing is when when the moduleName is not found it seems to cache that error,
so that even when the C-library is installed into the correct location it continues to not find the function.
I should have added this to the bug tracker a while ago, but I haven't checked for a while so I don't know if this is still the case.
I'll wait your response and if agreeable I'll add it to the P8 bug tracker.
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