🚀 go-pugleaf

In article <36B5EA0E.2361@imag.fr>, Yves Dufournaud wrote:
>
> I'am loading a file dynamic.o using dlopen
> this file is c++ with global object inside.
> but when I load it with a dlopen and using RTLD_NOW
> constructor of global object are not called.
>

 They should be. Global constructors are called from special
initialization hooks in an ELF shared library.

>
> I've compiled it using 
> g++ -shared dynamic.cc -export-dynamic
>

 Please try

  g++ -fPIC -c dynamic.cc
  g++ -fPIC -o dynamic.so dynamic.o

 This works for me. You also should upgrade your compiler. Gcc 2.7.2
has some serious drawbacks when building shared libraries. Try gcc
2.8.x or egcs 1.1.x.

	Frank

-- 
 + Frank Pilhofer                        fp@informatik.uni-frankfurt.de  +
 |                                      http://www.uni-frankfurt.de/~fp/ |
 +---- Life would be a very great deal less weird without you.  - DA ----+

In article <36B5EA0E.2361@imag.fr>,
  Yves Dufournaud <Yves.Dufournaud@imag.fr> wrote:
> Hi,
>
> I'am trying basic things using dlopen with g++-2.7.2.3 on sunos 5.5 :
>
> I'am loading a file dynamic.o using dlopen
> this file is c++ with global object inside.
>
> I've compiled it using
> g++ -shared dynamic.cc -export-dynamic
>
> but when I load it with a dlopen and using RTLD_NOW
> constructor of global object are not called.
>
> I don't understand why (my version of g++ generate elf) ?
>
> please help,
>
> thanks,
>
> Yves.
>
> --
> Yves Dufournaud Email Yves.Dufournaud at imag.fr equipe MOVI laboratoire
> GRAVIR
> --
>
Constructors for global objects are called from global initialization routine
typically caled crtbegin.o, which is linked into the ELF file when it
contains function "main". If you use dlsym and dlopen, to invoke the
routine, your program will not call constructors for the global objects in
that shared object. The only way to initialize global objects specified in
the shared library is to invoke some kind of explicit creation routine and
initialize them manually. That means to include routine named "InitMyGlobals"
in the shared library and then use dlopen to open it and then dlsym to get
the symbol you are looking for.
Mladen Gogala

-----------== Posted via Deja News, The Discussion Network ==----------
http://www.dejanews.com/       Search, Read, Discuss, or Start Your Own    

Yves Dufournaud <Yves.Dufournaud@imag.fr> writes:

>I'am trying basic things using dlopen with g++-2.7.2.3 on sunos 5.5 :
>but when I load it with a dlopen and using RTLD_NOW
>constructor of global object are not called.

Isn't this a known bug with sunos? You could always
find the initialisation routine and call it manually
I suppose.

Steve.
-- 
Stephen Kennedy -- Stephen.Kennedy@cs.tcd.ie

[[ PLEASE DON'T SEND ME EMAIL COPIES OF POSTINGS ]]

Steve<_s_t_e_v_e_@maths.tcd.ie> no underscores writes:

>Yves Dufournaud <Yves.Dufournaud@imag.fr> writes:

>>I'am trying basic things using dlopen with g++-2.7.2.3 on sunos 5.5 :
>>but when I load it with a dlopen and using RTLD_NOW
>>constructor of global object are not called.

>Isn't this a known bug with sunos? You could always
>find the initialisation routine and call it manually
>I suppose.

No, this works fine in Solaris 2.x (SunOS 5.x), which is what he is using.
You need to link with the compiler and probably with a newer version of
gcc/g++ too.

SunOS 4.x didn't implement init/fini routines, true but irrelevant

Casper
--
Expressed in this posting are my opinions.  They are in no way related
to opinions held by my employer, Sun Microsystems.
Statements on Sun products included here are not gospel and may
be fiction rather than truth.

Casper H.S. Dik - Network Security Engineer wrote:
> 
> [[ PLEASE DON'T SEND ME EMAIL COPIES OF POSTINGS ]]
> 
> Steve<_s_t_e_v_e_@maths.tcd.ie> no underscores writes:
> 
> >Yves Dufournaud <Yves.Dufournaud@imag.fr> writes:
> 
> >>I'am trying basic things using dlopen with g++-2.7.2.3 on sunos 5.5 :
> >>but when I load it with a dlopen and using RTLD_NOW
> >>constructor of global object are not called.
> 
> >Isn't this a known bug with sunos? You could always
> >find the initialisation routine and call it manually
> >I suppose.
> 
> No, this works fine in Solaris 2.x (SunOS 5.x), which is what he is using.
> You need to link with the compiler and probably with a newer version of
> gcc/g++ too.

I've followed the advice that many of you gave me : that is trying
to use a newer version of g++.

It seems that using the new version ( I've tried both g++-2.8.1 and
egcs-?)
I can't compile my code due to unresolved reference :

In this case, the unresolved reference is a global symbol which must
stay in the caller code
(the one which do the dlopen call)

I see no reason why it couldn't be done, but then how can I build the
shared object without
resolving that reference at compile time. I've tried the -Ur flag, but
without much success.
When I do that I get many unresolved reference comming from the standard
lib, and their
is no object file produced.

Cheers,

Yves

--
Yves Dufournaud Email Yves.Dufournaud at imag.fr equipe MOVI laboratoire
GRAVIR
--

Yves Dufournaud wrote:
> 
> Casper H.S. Dik - Network Security Engineer wrote:
> >
> > [[ PLEASE DON'T SEND ME EMAIL COPIES OF POSTINGS ]]
> >
> > Steve<_s_t_e_v_e_@maths.tcd.ie> no underscores writes:
> >
> > >Yves Dufournaud <Yves.Dufournaud@imag.fr> writes:
> >
> > >>I'am trying basic things using dlopen with g++-2.7.2.3 on sunos 5.5 :
> > >>but when I load it with a dlopen and using RTLD_NOW
> > >>constructor of global object are not called.
> >
> > >Isn't this a known bug with sunos? You could always
> > >find the initialisation routine and call it manually
> > >I suppose.
> >
> > No, this works fine in Solaris 2.x (SunOS 5.x), which is what he is using.
> > You need to link with the compiler and probably with a newer version of
> > gcc/g++ too.
> 
> I've followed the advice that many of you gave me : that is trying
> to use a newer version of g++.

OK, I've managed to do what I wanted :

You are right there is a bug in g++-2.7.x and that why I got this
behavior.

Now it compiles fine using g++-2.8.1 (I haven't try egcs).

The problem I was having with other globals not resolved, were solved
using the  -Ur flag for compilation in conjunction with RTLD_GLOBAL
in the dlopen function.

So it works fine now,

thank you for your help.

Cheers,

Yves.

--
Yves Dufournaud Email Yves.Dufournaud at imag.fr equipe MOVI laboratoire
GRAVIR
--

In comp.unix.programmer mgogala@yahoo.com wrote:
> In article <36B5EA0E.2361@imag.fr>,
>   Yves Dufournaud <Yves.Dufournaud@imag.fr> wrote:
>> Hi,
>>
>> I'am trying basic things using dlopen with g++-2.7.2.3 on sunos 5.5 :
>>
>> I'am loading a file dynamic.o using dlopen
>> this file is c++ with global object inside.
>>
>> I've compiled it using
>> g++ -shared dynamic.cc -export-dynamic
>>
>> but when I load it with a dlopen and using RTLD_NOW
>> constructor of global object are not called.
>>
>> I don't understand why (my version of g++ generate elf) ?
>>
>> please help,
>>
>> thanks,
>>
>> Yves.
>>
>> --
>> Yves Dufournaud Email Yves.Dufournaud at imag.fr equipe MOVI laboratoire
>> GRAVIR
>> --
>>
> Constructors for global objects are called from global initialization routine
> typically caled crtbegin.o, which is linked into the ELF file when it
> contains function "main". If you use dlsym and dlopen, to invoke the
> routine, your program will not call constructors for the global objects in
> that shared object. The only way to initialize global objects specified in
> the shared library is to invoke some kind of explicit creation routine and
> initialize them manually. That means to include routine named "InitMyGlobals"
> in the shared library and then use dlopen to open it and then dlsym to get
> the symbol you are looking for.
> Mladen Gogala

Yep.. That's the problem.  You can make the function mentioned (BTW, you'll
have to extern "C" so dlsym will find it due to C++ name mangling).

There is another option.  I understand in ELF, you have the .init and .fini
sections which are called automagically on loading or dlopen().  I've played
with the on Linux and I understand it's an ELF-thing.  :)

It has been a while but I believe this translates into:

extern "C" {
void init(void);
void fini(void);
}

// Create a tradition-like global initializer.

MyClass &obj;

void init(void)
{
    MyClass *o = new MyClass();

    ASSERT( o != NULL );
    obj = &o;
}

void fini(void)
{
    MyClass *o = &obj;

    delete o;
}

	Hope this helps,
		Dan
-- 
 Dan Miner    dminer@nyx.net |                                        | Doing
         Programmer/         |                                        | Linux
      Linux Consultant       | "What yonder light Windows 95 breaks?" | since
 http://www.nyx.net/~dminer/ |    "Free software: The New Frontier"   | v0.12

In article <918255234.345483@iris.nyx.net>,
  Dan Miner <dminer@nyx.net> wrote:
> In comp.unix.programmer mgogala@yahoo.com wrote:
> > In article <36B5EA0E.2361@imag.fr>,
> >   Yves Dufournaud <Yves.Dufournaud@imag.fr> wrote:
> >> Hi,
> >>
> >> I'am trying basic things using dlopen with g++-2.7.2.3 on sunos 5.5 :
> >>
> >> I'am loading a file dynamic.o using dlopen
> >> this file is c++ with global object inside.
> >>
> >> I've compiled it using
> >> g++ -shared dynamic.cc -export-dynamic
> >>
> >> but when I load it with a dlopen and using RTLD_NOW
> >> constructor of global object are not called.
> >>
> >> I don't understand why (my version of g++ generate elf) ?
> >>
> >> please help,
> >>
> >> thanks,
> >>
> >> Yves.
> >>
> >> --
> >> Yves Dufournaud Email Yves.Dufournaud at imag.fr equipe MOVI laboratoire
> >> GRAVIR
> >> --
> >>
> > Constructors for global objects are called from global initialization
routine
> > typically caled crtbegin.o, which is linked into the ELF file when it
> > contains function "main". If you use dlsym and dlopen, to invoke the
> > routine, your program will not call constructors for the global objects in
> > that shared object. The only way to initialize global objects specified in
> > the shared library is to invoke some kind of explicit creation routine and
> > initialize them manually. That means to include routine named
"InitMyGlobals"
> > in the shared library and then use dlopen to open it and then dlsym to get
> > the symbol you are looking for.
> > Mladen Gogala
>
> Yep.. That's the problem.  You can make the function mentioned (BTW, you'll
> have to extern "C" so dlsym will find it due to C++ name mangling).
>
> There is another option.  I understand in ELF, you have the .init and .fini
> sections which are called automagically on loading or dlopen().  I've played
> with the on Linux and I understand it's an ELF-thing.  :)
>
> It has been a while but I believe this translates into:
>
> extern "C" {
> void init(void);
> void fini(void);
> }
>
> // Create a tradition-like global initializer.
>
> MyClass &obj;
>
> void init(void)
> {
>     MyClass *o = new MyClass();
>
>     ASSERT( o != NULL );
>     obj = &o;
> }
>
> void fini(void)
> {
>     MyClass *o = &obj;
>
>     delete o;
> }
>
> 	Hope this helps,
> 		Dan
> --
>  Dan Miner    dminer@nyx.net |                                        | Doing
>          Programmer/         |                                        | Linux
>       Linux Consultant       | "What yonder light Windows 95 breaks?" | since
>  http://www.nyx.net/~dminer/ |    "Free software: The New Frontier"   | v0.12
>
Now this is a neat trick! I'll try it from Intel Solaris and let you
know if it works. Thanks again!

Mladen Gogala

-----------== Posted via Deja News, The Discussion Network ==----------
http://www.dejanews.com/       Search, Read, Discuss, or Start Your Own