[Vm-dev] Fwd: loading library with FFI fails (was [Pharo-project] Linux vm: assertions and strategy)

laurent laffont laurent.laffont at gmail.com
Fri Apr 9 06:15:12 UTC 2010


Hi,

it seems that on Linux loading a library with FFI fails (rev 2135 -> rev
2151). Bill submit a patch below.

Is this a known problem ?

Furthermore, the Linux VM I've built for Pharo is rev. 2151 with 2 patchs
(found on this mailing list)
- http://lolgzs.free.fr/pharo/ft2plugin.patch so FT2Plugin can be built
- http://lolgzs.free.fr/pharo/CFLAGS.patch for multiple CFLAGS options  to
work

Are the above issues fixed in current trunk ? Maybe I forgot to read
important things, it's not clear for me how to report bugs on squeak-vm and
how to submit patchs...

Cheers,

Laurent Laffont


---------- Forwarded message ----------
From: Schwab,Wilhelm K <bschwab at anest.ufl.edu>
Date: Fri, Apr 9, 2010 at 12:11 AM
Subject: Re: [Pharo-project] Linux vm: assertions and strategy
To: "Pharo-project at lists.gforge.inria.fr" <
Pharo-project at lists.gforge.inria.fr>


Laurent,

The promised code for tryLoadModule(); it goes just before

 if (!handle) {
   struct stat buf;
   if ((0 == stat(path, &buf)) && ! S_ISDIR(buf.st_mode))
     fprintf(stderr, "%s\n", dlerror());
 }
 return handle;

Drop the fprintf() calls if you want - I know what was happening now?

Bill

========================


 /*
   wks - have not loaded a library?  Is the path absolute?  Use the name as
given.
 */
 if( (!handle) && ( (int)(name[0])==47 ) )
 {
    handle=dlopen(name, RTLD_NOW | RTLD_GLOBAL);
    fprintf(stdout,"WKS-load-by-name(%s) = %p\n", path,handle);
 }
 else {
    if(!handle){
       fprintf(stdout,"WKS-refuse-load-by-name(%s) - not absolute path\n",
path);
    }
 }



________________________________________
From: pharo-project-bounces at lists.gforge.inria.fr [
pharo-project-bounces at lists.gforge.inria.fr] On Behalf Of Schwab,Wilhelm K [
bschwab at anest.ufl.edu]
Sent: Thursday, April 08, 2010 6:10 PM
To: Pharo-project at lists.gforge.inria.fr
Subject: Re: [Pharo-project] Linux vm: assertions and strategy

Laurent,

A part-time boss/full-time friend once advised me to "get the machine to
tell you what it's doing" (I was doing just that at the time, but I've never
forgotten his advise<g>).

I compiled your vm and then decided to stick some tracing code in strategic
places to find what the vm thinks it is doing in trying to load unixODBC.
 Get ready:

    tryLoading(/sr/local/slib/squeak/3.11.13-/so.libodbc.so) = (nil)

In short, it does not appear to recognize a difference between plugins (the
names of which it twists around to avoid collisions with external libraries
- that's fine) and external libraries that have been minding their own
business for many clock cycles.  The latter deserve special attention.

So I had an absolutely nutty idea: give dlopen() the name of the library as
written :)  Clearly, that works only if one provides an absolute path in
#moduleName, but (forgive/correct possible *nix-noob syndrome here) that is
easy to test and even easier to do in the code.

So, in sqUnixExternalPrims.c in the unix/vm directory, look near the end of
tryLoadModule().  My proposed workaround is to add some code before the
!handle test at the end.  I will send a cut-down version of it in a separate
email.  Unless someone has a better idea, I suggest we make this change to
you source to give people an opportunity to use external libraries: (1) I
fear at all(!!); (2) by absolute path if desired.

BTW, the 3.11-3 vm indeed appears to have fixed my problem w/ double return
values, at least the boiled-down test works.

Bill


________________________________
From: pharo-project-bounces at lists.gforge.inria.fr [mailto:
pharo-project-bounces at lists.gforge.inria.fr] On Behalf Of laurent laffont
Sent: Thursday, April 08, 2010 3:22 PM
To: Pharo-project at lists.gforge.inria.fr
Subject: Re: [Pharo-project] Linux vm: assertions and strategy

2010/4/8 Schwab,Wilhelm K <bschwab at anest.ufl.edu<mailto:
bschwab at anest.ufl.edu>>
Laurent,

I was reading a little about Eliot's proposed FPU init changes to FFI and
then took another look at your evolving Pharo vm source and I was struck by
either: (1) a brilliant (well, fairly clever) workaround to my external
library hassles; (2) a completely and totally stupid idea.

You have based the vm on the 3.11-3 sources, so it hopefully fixes the
double return defect that has been driving me nuts.  My remaining problem is
to get the vm to load external libraries.  Would a simple plugin to expose
dlopen() (and perhaps dlsym() while we're at it) solve the problem?  I
should then be able to bypass the FFI code that calls dlopen() (I suspect
that it's pretty badly broken) by setting the handle of any ailing library
by using absolute paths if necessary.  From there, I *think* everything will
just work.

What do you think?

Well, I'm noob on VM stuff, I've just worked on how to generate VM source
for Linux, that's all :)  So I cannot tell anything...I have to learn
before.



Somewhat related, have you looked at compiling the Alien plugin?  The more I
look at posts on Alien, the more I wonder whether it will help, as there are
suggestions that it is weak on external calls.  Still, it would be nice to
get it going and look over the tests the boldness that comes from watching
them pass having actually done something.

Yes I can compile it, but the VM crashes loudly when trying to use it.  This
thread has a lot of informations:
http://n4.nabble.com/Trying-to-build-alien-plugin-in-linux-tc1562896.html



Laurent Laffont


Bill


________________________________
From: pharo-project-bounces at lists.gforge.inria.fr<mailto:
pharo-project-bounces at lists.gforge.inria.fr> [mailto:
pharo-project-bounces at lists.gforge.inria.fr<mailto:
pharo-project-bounces at lists.gforge.inria.fr>] On Behalf Of laurent laffont
Sent: Thursday, April 08, 2010 7:32 AM
To: Pharo-project at lists.gforge.inria.fr<mailto:
Pharo-project at lists.gforge.inria.fr>
Subject: Re: [Pharo-project] Linux vm: assertions and strategy


I'm totally noob on FFI. Maybe the vm-dev mailing list is more appropriate ?
 It seems there's actually some problems with it
http://n4.nabble.com/forum/Search.jtp?tpl=search-page&node=104410&query=ffi

On my machine, 20/21 FFI unit tests fails...

I haven't been able to build last revision of squeak-vm trunk.

Laurent Laffont


On Thu, Apr 8, 2010 at 1:53 PM, Schwab,Wilhelm K <bschwab at anest.ufl.edu
<mailto:bschwab at anest.ufl.edu>> wrote:
Laurent, all,

If I may jump to conclusions a little, the 3.11-3 vm's changes break the
loading of libraries, certainly to the point of being arkane.  Beyond that,
LinuxODBC is transparent to it, so I am left wondering how it is suppose to
work at all??

The RC3 one-click image and vm produce very nice fonts on my Ubuntu laptop,
but it retains the FFI/double defect, and from the naming of the plugins,
must be based on a pre 3.11-3 vm.

Is the plan to use 3.11-3 for the one-click?  If so, we need to do something
about external libraries; at a minimum, LinuxODBC should work, whether by
fully understanding how to use environment variables, or (as I suspect)
getting the dlopen() call to work again.

Another option is to identify the FPU related fixes and apply them to the
current one-click vm.

Any preferences?  Any success with 3.11-3 and LinuxODBC?  I'd be happy to be
wrong about this.

Bill


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