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

[raymond@cdlsystems.com]

>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:
----gnatsweb-attachment----
Content-Type: application/x-zip-compressed; name="dynamiccast.zip"
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename="dynamiccast.zip"
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