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To: Robert Boehne <rboehne@ricardo-us.com>
cc: gcc@gcc.gnu.org
Subject: Re: AIX g++ 3.0.2 Undefined symbol: virtual thunk to... 
In-Reply-To: Message from Robert Boehne <rboehne@ricardo-us.com> 
   of "Thu, 06 Dec 2001 11:20:26 CST." <3C0FA8DA.945EEA50@ricardo-us.com> 
Date: Thu, 06 Dec 2001 09:55:00 -0000
From: David Edelsohn <dje@watson.ibm.com>
X-SW-Source: 2001-12/txt/msg00289.txt.bz2

>>>>> Robert Boehne writes:

Robert> Now I'm baffled.  If g++ isn't generating them, how do they get
Robert> into my object code?  Doing an nm of this library I get 68 lines
Robert> that match "thunk".
Robert> nm ./sigc++/.libs/libsigc.a | c++filt | grep thunk
Robert> 000000001004b668 t .non-virtual thunk to std::iostream::~iostream()
Robert> <SNIP>
Robert> 0000000020010e48 d virtual thunk to std::strstream::~strstream()
Robert> 0000000020010ca4 d virtual thunk to SigC::Object::~Object()
Robert> 0000000020010c98 d virtual thunk to
Robert> SigC::Object::~Object()                                                                                  

Robert> Are you saying that some other compiler is generating these?
Robert> My suspicion is that it is related to having a compiler configured
Robert> with "--disable-shared --disable-threads" so I'm working on
Robert> re-bootstrapping gcc with "--enable-threads=posix --enable-shared".
Robert> I'm not sure what a "thunk" is so the link error doesn't help
Robert> me much.

	I do not know what a virtual thunk is.

	Thunks are described on many websites.  It is a piece of code to
fix up the "this" pointer for multiple inheritance.

	Maybe some part of GCC is not obeying #ifdef ASM_OUTPUT_MI_THUNK.

David