My point was that anything you do in Pharo will lower performance quite a bit, but it wont be noticable anyway unless its in a big loop or something. Second that Pharo cannot debug such issues which is a huge deal when you work with OS stuff and OS calls. You are far better doing this outside UFFI and straight inside a C IDE because you will have an army of tools that will make your life a ton easier. Hence why I talked about performance, C coding and Pharo crashes. In my case I had to write and test the code in C to port it to UFFI because it was impossible to resolve the bugs from inside Pharo. Also crashing Pharo all the time got really annoying and I managed to corrupt a couple of images too in the process. Of course debugging C code from a C IDE is quite similar to how you work with Pharo. I also got an experience with loading libraries because I worked with Shared memory mapped files which is the technology OS uses to load DLLs. Its really low level stuff that come directly from OS kernel. It was a ton of fun. Also C is easier because obviously there is a ton of docs and all you have to do is copy paste. In case of UFFI you have to first figure out the C code and then how to convert it to UFFI so its double the effort for little gain. Its much better thing to just wrap C code and minimize the usage of UFFI. The benefits of Pharo are lost anyway as soon as you drop so low level. On Thu, Mar 16, 2017 at 3:05 PM <raffaello.giulietti@lifeware.ch> wrote:
Indeed, experimenting using some combination of AddDllDirectory(), SetDllDirectory() and LoadLibraryEx() was in my plan for next week.
Thanks
On 16/03/17 11:59, Mark Bestley wrote:
Yes the calling process can alter where these indirect DLLs are loaded from and so should be able to be done in UFFI and directly from Smalltalk
The OS will load the DLL specified then it runs DllMain and doing that causes the OS to load any DLLs that it calls
MSDN https://msdn.microsoft.com/en-us/library/7d83bc18.aspx says
With both implicit and explicit linking, Windows first searches for "known DLLs", such as Kernel32.dll and User32.dll. Windows then searches for the DLLs in the following sequence: The directory where the executable module for the current process is located. The current directory. The Windows system directory. The GetSystemDirectory function retrieves the path of this directory. The Windows directory. The GetWindowsDirectory function retrieves the path of this directory. The directories listed in the PATH environment variable.
This can be changed using the call LoadLibraryEx instead of LoadLibrary Flags can be set to change the directories used
https://msdn.microsoft.com/en-us/library/windows/desktop/ms684179(v=vs.85).a...
Also see AddDllDirectory
https://msdn.microsoft.com/en-us/library/windows/desktop/hh310513(v=vs.85).a...
Mark
On 15/03/2017 17:22, Raffaello Giulietti wrote:
Hi Dimitris,
I don't get your point about proper C coding, C performance or Pharo crashes. It is not the focus of this thread.
How dependencies between libraries are resolved at load-time is dictated by the OS. If the OS offers a working mechanism to specify folders that the OS uses to search for libraries at load-time, well, I think that Pharo, hence the UFFI, should offer it as well and in a more fashionable format. UFFI is quite elegant in many respects but I wouldn't call it a minimalist design (zero hand holding, if I understand you correctly). But I'm happy the extra elegance is there because it makes life more comfortable.
Again, I still have to experiment with SetDllDirectory() in the case of Windows, so I'm not in a position to say something authoritative yet.
On 2017-03-15 17:41, Dimitris Chloupis wrote:
Please note the moment you use a FFI of any language you step to a C territory. VMs tend not to touch the code because the code is already in machine code format.
There is zero reason for UFFI to worry about the dependencies of a library loaded, this must happen at the library level that UFFI does not focus on.
What you describe here is standard practice because the vast majority of libraries depend on other libraries. In the end UFFI or any FFI in any language is not there to replace proper C coding but rather to allow you to utilize C libraries. You cannot hope to achieve performance comparable to C if you try to use a language that is not C to do standard things like dependency management.
If the library fail to load it wont be because of UFFI it will be because the library is buggy at handling its dependencies. That means that the library will be buggy even if you use it from C directly.
Even you do not know what you doing at C level, you going to crash Pharo countless times anyway and the least of your worries will be handling dependencies which far more obvious than some other nasty C bugs.
I think its a great idea that UFFI does zero hand holding. This way it gives the clear message that if you do not understand C then you should not be using the UFFI in the first place.
On Wed, Mar 15, 2017 at 4:51 PM Esteban Lorenzano <estebanlm@gmail.com <mailto:estebanlm@gmail.com>> wrote:
> On 15 Mar 2017, at 15:44, Raffaello Giulietti <raffaello.giulietti@lifeware.ch <mailto:raffaello.giulietti@lifeware.ch>> wrote: > > On 2017-03-15 15:20, Esteban Lorenzano wrote: >> >>> On 15 Mar 2017, at 15:08, Raffaello Giulietti <raffaello.giulietti@lifeware.ch <mailto:raffaello.giulietti@lifeware.ch>> wrote: >>> >>> Hi Esteban, >>> >>> I understand this is the current status of the UFFI, so I can certainly use the workarounds discussed below. >>> >>> But I hope UFFI will soon offer a more "declarative" way to specify the search folders, kind of LD_LIBRARY_PATH mechanism but in the UFFI. >> >> that will NOT solve the problem of dependencies of libraries indirectly references. >> There is no way to do that (indirect reference solving) on an executing program that I know. >> So is not âcurrent status of UFFIâ: it will never provide that. >> > > Do you mean that SetDllDirectory() has no influence when invoked between Pharo's start and the LoadLibrary() call done by the UFFI?
I really have no idea. You can try to add it to your app.
Esteban
> > > > >> All that, unless someone come and says: "look, Esteban is like thisâ. >> >> I spent last three weeks (not full time of course) trying to do exactly that for our current linux vm, to force libgit2 to use the version of libssh2 we want (and not the version on system)⦠and I failed. I solved some cases, but not all. So at the end I opted to change zeroconf to define LD_LIBRARY_PATH before calling pharo. Only way I found I can force the lookup paths. >> >> cheers, >> Esteban >> >>> >>> >>> >>> Greetings >>> Raffaello >>> >>> >>> >>> >>> On 2017-03-15 14:52, Esteban Lorenzano wrote: >>>> Hi, >>>> >>>> UFFI cannot do what you want. >>>> If I understand well, you have: >>>> >>>> Pharo -> libA.dll -> libB.dll >>>> >>>> Pharo does a LoadLibrary(libA.dll), but has no control on how libA calls libB⦠and is not possible for us to influence it more than the predefined platform ways. >>>> >>>> One posible workaround (just possible, no idea if it will work) is to perform a load of libB before is required by libB. Then hopefully the loader will understand is same library and will answer same handler (but not sure, because if it discriminates by path⦠then youâre in the same position). Anyway, if you want to try it, it would be something like this: >>>> >>>> DynamicLoader loadLibrary: 'path/to/libB.dllâ. >>>> DynamicLoader loadLibrary: 'path/to/libA.dllâ. >>>> >>>> then you can try to execute functions of libA⦠>>>> >>>> cheers, >>>> Esteban >>>> >>>> >>>>> On 15 Mar 2017, at 14:32, Raffaello Giulietti <raffaello.giulietti@lifeware.ch <mailto:raffaello.giulietti@lifeware.ch>> wrote: >>>>> >>>>> On 2017-03-15 13:51, Ben Coman wrote: >>>>>> >>>>>> >>>>>> On Wed, Mar 15, 2017 at 4:42 PM, Raffaello Giulietti >>>>>> <raffaello.giulietti@lifeware.ch <mailto:raffaello.giulietti@lifeware.ch> >>>>>> <mailto:raffaello.giulietti@lifeware.ch <mailto:raffaello.giulietti@lifeware.ch>>> wrote: >>>>>> >>>>>> Hi Ben, >>>>>> >>>>>> my understanding is that SetDllDirectory only affects the search >>>>>> path of libraries that are loaded at *run-time* with LoadLibrary. >>>>>> >>>>>> What I'm asking for is a mechanism that works at *load-time*, when a >>>>>> library I'm accessing directly depends on another one which I'm not >>>>>> targeting directly. >>>>>> >>>>>> >>>>>> I don't quite follow. I'm not intimate with Windows dynamic loading, so >>>>>> these questions are an opportunity for me to learn... >>>>>> >>>>>> You can't mean when Pharo loads, because it wouldn't know of OTHER.DLL ? >>>>>> >>>>>> Do you mean that LoadLibrary is not called explicitly by YOUR.DLL before >>>>>> its uses the function from OTHER.DLL? >>>>>> >>>>> >>>>> During the build of YOUR.DLL, you can specify that it should depend on OTHER.LIB (kind of binary which lists function headers and static data declarations for OTHER.DLL). Linking resolution is then done at load-time of YOUR.DLL, not by invoking LoadLibrary("OTHER.DLL"). >>>>> >>>>> When YOUR.DLL is loaded by UFFI at run-time (here by means of LoadLibrary(), I guess), Windows (not the UFFI) also attempts to load OTHER.DLL because of the linking information gathered during the build. Notice that the linking information does *not* include a specific path for OTHER.DLL. >>>>> >>>>> (You don't have to mention standard *.LIBs like Kernel32.lib because they are included by default. But of course, Windows knows where to find the corresponding .dll.) >>>>> >>>>> OTHER.DLL is searched using the strategy described in the MSDN page you mention. My expectation is/was that UFFI has/had an API for specifying the search paths where to find OTHER.DLL in a platform-independent way. In other words, I would expect the UFFI to do the call of SetDllDirectory() or whatever is needed on Windows for me or to use other mechanisms on other platforms. >>>>> >>>>> >>>>> >>>>>> Do you mean you link OTHER.DLL to YOUR.DLL at compile time? >>>>>> But still, YOUR.DLL it not loaded until called via Pharo FFI, so neither >>>>>> is OTHER.DLL, >>>>>> and Dynamic-Link Library Search Order [1] says... "If a DLL with the >>>>>> same module name >>>>>> is already loaded in memory, the system uses the loaded DLL, no matter >>>>>> which directory it is in. >>>>>> The system does not search for the DLL." >>>>>> >>>>>> So maybe before calling any of YOUR.DLL, >>>>>> do a SetDllDirectory followed by a LoadLibrary(OTHER.DLL) >>>>>> and later when you call into YOUR.DLL, >>>>>> OTHER.DLL is already loaded. >>>>>> >>>>> >>>>> Yes, this might work but is rather contrived. >>>>> >>>>> >>>>> >>>>>> Otherwise it would seems(?) your options are either
Manifests
>>>>>> or Dynamic-Link Library Redirection, both done outside of Pharo. >>>>>> >>>>> >>>>> What if neither YOUR.DLL nor OTHER.DLL are under my control? The only thing I know is where the .dll and the corresponding .lib + .h are. >>>>> >>>>> >>>>> >>>>> Thanks for your interest >>>>> Raffaello >>>>> >>>>> >>>>> >>>>> >>>>>> But I'll try whether SetDllDirectory also affects load-time searches. >>>>>> >>>>>> Anyway, I hope future versions of the UFFI to offer setting the >>>>>> search paths more easily. >>>>>> >>>>>> >>>>>> >>>>>> Greetings >>>>>> Raffaello >>>>>> >>>>> >>>>> >>>> >>>> >>> >>> >> >> > >