[Bug c++/39494] New: Bad assembly when derived class has same name as virtual method

[Bug c++/39494] New: Bad assembly when derived class has same name as virtual method

[james dot ashley at gmail dot com]

I'm sorry...I don't know what "triplet" means.  There was nothing about it in
the FAQ. I took my best guess.

g++ -v --version prints
g++ (Debian 4.3.2-1.1) 4.3.2

cat /proc/version prints
Linux version 2.6.26-1-686 (Debian 2.6.26-13) (waldi@debian.org) (gcc version
4.1.3 20080704 (prerelease) (Debian 4.1.2-24)) #1 SMP Sat Jan 10 18:29:31 UTC
2009

I'm using the stock g++ build that came from Debian, whatever compiler options
they use.

After I traced it down, the problem turned out to be fairly simple  [to
produce].

In what looks [to me] like the vtable for the constructor of the derived class,
the compiler's appending *INTERNAL*.

Since I don't know whether there's a page 2,

The command  gcc -c -Wall compilerBug.cpp

produces the output 

/tmp/ccHFsjIR.s: Assembler messages:
/tmp/ccHFsjIR.s:68: Warning: missing operand; zero assumed
/tmp/ccHFsjIR.s:68: Error: undefined symbol `INTERNAL' in operation

The line it's complaining about looks like this:
        .long   _ZN7DerivedC1Ev *INTERNAL* 

I've boiled the precompiled source file down to

# 1 "compilerBug.cpp"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "compilerBug.cpp"
class Base
{
   public:
      virtual void Derived() = 0;
};

class Derived : public Base
{
   public:
      Derived();
};

Derived::Derived()
   : Base()
{}

(Everything else I tried to delete let the compiler optimize everything away).

I have no idea what the standard says about how this should actually work (or
not). Compiler error about conflicting symbols?  Warning about "this is stupid,
and you probably don't want to do it"? Or just go ahead and magically work?

Especially since the work-around's as easy as renaming either the function or
the derived class.

I just know that the FAQ says that invalid assembly output is a bug, so here we
go.

Thanks *so* much for committing time and effort to work on the compiler. It
really is the heart and soul of the entire free software movement.


-- 
           Summary: Bad assembly when derived class has same name as virtual
                    method
           Product: gcc
           Version: 4.3.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: james dot ashley at gmail dot com
 GCC build triplet: 4.3.2
  GCC host triplet: 2.6.26-13
GCC target triplet: 2.6.26-13


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39494

[Bug c++/39494] Bad assembly when derived class has same name as virtual method

[james dot ashley at gmail dot com]

------- Comment #1 from james dot ashley at gmail dot com  2009-03-18 14:33 -------
Created an attachment (id=17487)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=17487&action=view)
Smallest example I could come up with

Sorry, like I said in the description, I wasn't sure I'd have a chance to do
this


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39494

[Bug c++/39494] Bad assembly when derived class has same name as virtual method

[rguenth at gcc dot gnu dot org]

------- Comment #2 from rguenth at gcc dot gnu dot org  2009-03-18 14:56 -------
This means that a reference to an abstract function is emitted which should
have been cloned.  EDG accepts this testcase so I qualify this as wrong-code
bug.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
           Keywords|                            |rejects-valid, wrong-code
      Known to fail|                            |3.3.6 4.0.0 4.3.3 4.4.0
   Last reconfirmed|0000-00-00 00:00:00         |2009-03-18 14:56:55
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39494

[Bug c++/39494] Bad assembly when derived class has same name as virtual method

[hjl dot tools at gmail dot com]

------- Comment #3 from hjl dot tools at gmail dot com  2009-03-18 16:16 -------
Icc ia32 generates:

_ZTV7Derived:
        .type   _ZTV7Derived,@object
        .size   _ZTV7Derived,12
        .long   0   
        .long   _ZTI7Derived
        .long   __cxa_pure_virtual

Gcc generates:

        .size   _ZTV7Derived, 24
_ZTV7Derived:
        .long   0
        .long   _ZTI7Derived
        .long   __cxa_pure_virtual
        .long   _ZN7DerivedC1Ev *INTERNAL*
        .long   _ZN7DerivedC2Ev
        .long   _ZN7DerivedC1Ev


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39494

[Bug c++/39494] Bad assembly when derived class has same name as virtual method

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=39494

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|gcc-bugs at gcc dot gnu.org        |
      Known to work|                            |4.10.0, 4.8.0, 4.9.0
         Resolution|---                         |FIXED
      Known to fail|                            |

--- Comment #4 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Fixed long time ago.