c++/9796: dynamic cast in shared library failed

c++/9796: dynamic cast in shared library failed

[raymond]

>Number:         9796
>Category:       c++
>Synopsis:       dynamic cast in shared library failed
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Feb 22 00:06:01 UTC 2003
>Closed-Date:
>Last-Modified:
>Originator:     raymond@cdlsystems.com
>Release:        GCC 3.2
>Organization:
>Environment:
linux
>Description:
When a class is created in the main function and passing it off to a shared library for downcasting, dynamic cast returns null.  

typedef void ( *PFN )( Parent* );

int main()
{
   Parent parent;
   Child child;
   void* pDl = dlopen ( "libshared.so",  
                        RTLD_GLOBAL|RTLD_NOW);
   PFN pfnAcquire = ( PFN )dlsym( pDl, "function1" );

   printf( "before %x %x\n", &child,  dynamic_cast<Child*>( &child ));
   pfnAcquire( &child );
}

In the acquired function from the shared library, if the same dynamic cast operation is done again, the result is always null.

When compiling the so file, -Wl,-E is used. See the attached script
 
>How-To-Repeat:
use the provided script to recompile the program and run it.
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted:
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Re: c++/9796: dynamic cast in shared library failed

[bangerth]

Synopsis: dynamic cast in shared library failed

State-Changed-From-To: feedback->open
State-Changed-By: bangerth
State-Changed-When: Mon Feb 24 19:15:12 2003
State-Changed-Why:
    Feedback provided.
    
    Needs someone with knowledge of shared libraries and ldopen
    to investigate.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=9796

Re: c++/9796: dynamic cast in shared library failed

[bangerth]

Synopsis: dynamic cast in shared library failed

State-Changed-From-To: open->feedback
State-Changed-By: bangerth
State-Changed-When: Sat Feb 22 00:31:58 2003
State-Changed-Why:
    You didn't say which platform this is on. I guess, it is
    SPARC/Solaris, right? If so, we have about half a dozen
    such reports. It would be really helpful if the sparc
    maintainers could look at them eventually...

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=9796