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From: "samuel_benjamin at mentor dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c++/98436] New: issue with casting member function on linux32
 bit only
Date: Thu, 24 Dec 2020 09:19:05 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D98436

            Bug ID: 98436
           Summary: issue with casting member function on linux32 bit only
           Product: gcc
           Version: 7.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: samuel_benjamin at mentor dot com
  Target Milestone: ---

Created attachment 49840
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D49840&action=3Dedit
TestCase

There is an issue with gcc 7.4.0 linux32 bit only, I tried the example below
with 4.7.4 , 5.3.0. 6.3.0 , all are working fine for both 32bit and 64 bit
except gcc-7.4.0 linux32.

The issue is i have an un-implemented member function in a class , and the
implementation is inside another stub file.

The main exe loads two shared librares ( systemc.so ) and (systemc_stubs.so=
) ,
the issue arrives when i casts the undefined member function pointer is :

on gcc-7.4.0- 32 bit :

(gdb) p tmp
$1 =3D &virtual table offset -134397620


on gcc-7.4.0 - 64 bit and many other gcc versions :=20
$1 =3D (void (functor::*)(functor * const)) 0x7ffff7e4c15a
     <_ZN7MyClass17myUndefinedMethodEv()>


Files are below :
Class.h --> basic class
testbench.cpp --> this is the main file for the fist so ( systemc.so)
stub.cpp --> systemc_stubs.so
main.cpp --> main exe which loads the 2 so and executes the entry point.

Compilation :
g++ -shared -o systemc.so -Wl,-E -Wl,-Bsymbolic -lm testbench.cpp -g
g++ -shared -o systemc_stubs.so -Wl,-E -Wl,-Bsymbolic -lm stub.cpp -g
g++ main.cpp -g -ldl -o testmain=