[cxx-abi-dev] Proposed clarification

[Mark Mitchell]

Mark Mitchell wrote:

> Presently, the ABI is not 100% clear about whether two member function 
> types for non-static member functions of different classes can be 
> substitution candidates.  For example, given:
> 
>  struct S {  };
>  struct T { };
> 
> would the function types pointed to be "void (S::*)()" and "void 
> (T::*)()" be the same type, for the purposes of substitution.
> 
> The EDG front end and G++ agree that they are not the same type, for the 
> purposes of substitution, and I believe that is consistent with the 
> spirit of the ABI, which already says that the types pointed to be "void 
> (*)()" and "void (S::*)()" are not the same type for the purposes of 
> substitution.
> 
> Therefore, I intend to update the ABI document with the attached change, 
> unless anyone objects.
> 
> Are there any objections?

There were no objections, so I committed the patch below, after fixing a 
typo therein.

It's been pointed out to me that there is another problem with the 
specification in this area, which I will attempt to address separately.


> ------------------------------------------------------------------------
> 
> Index: abi.html
> ===================================================================
> RCS file: /home/cvs/Repository/cxx-abi/abi.html,v
> retrieving revision 1.75
> diff -c -5 -p -r1.75 abi.html
> *** abi.html	28 Nov 2003 20:58:26 -0000	1.75
> --- abi.html	20 Feb 2004 07:57:01 -0000
> *************** No entity is added to the dictionary twi
> *** 4593,4602 ****
> --- 4593,4612 ----
>   
>   <p>
>   The type of a non-static member function is considered to be
>   different, for the purposes of substitution, from the type of a
>   namespace-scope or static member function whose type appears similar.
> + The types of two non-static member functions are considered to be
> + different, for the purposes of substitution, if the functions are
> + members of different classes.  In other words, for the purposes of
> + substitution, the class of which the function is a member is
> + considered part of the type of function.
> + </p>
> + 
> + <p>
> + <img src=warning.gif alt="<b>NOTE</b>:">
> + <i>
>   Therefore, in the following example:
>   <blockquote><code><pre>
>   typedef void T();
>   struct S {};
>   void f(T*, T (S::*)) {}
> *************** the function <code>f</code> is mangled a
> *** 4606,4615 ****
> --- 4616,4626 ----
>   to by the second parameter is not considered the same as the type of
>   the function pointed to by the first parameter.  Both function types
>   are, however, entered the substitution table; subsequent references to
>   either variant of the function type will result in the use of
>   substitutions.
> + </i></p>
>   
>   <p>
>   Substitution is according to the production:
>   
>   <pre><font color=blue><code>
> *************** unwind table location.
> *** 4913,4922 ****
> --- 4924,4938 ----
>   <p> <hr> <p>
>   
>   <p>This version of this document is $Revision: 1.75 $.  No special
>   significance should be attached to the form of the revision number; it
>   is simply a identifying number.</p>
> + 
> + <p>
> + <font color=blue>[040219}</font>
> + Clarify substition of member function types.
> + </p>
>   
>   <p>
>   <font color=blue>[031128]</font>
>   Fix alphabetization of company names.

-- 
Mark Mitchell
CodeSourcery, LLC
mark at codesourcery.com