Re: [patch/testsuite/cp] local.exp: accommodate gcc abi 2

[Andrew Cagney <cagney@gnu.org>]

> ac> Is this "The New ABI" or a yet to be named but for the moment would be 
> ac> best refered to as "The New New ABI"?
> 
> The former.
> 
> It's minor version 2 of "The New ABI", also known as "The IA-64 ABI".
> It contains small bug fixes to g++ to make it more compatible with
> the spec for "The New ABI".
> 
>   gcc 2.95.3	old abi

As daniel eluded to, there was an even earlier ABI (I've no idea of its 
history, I guess it was 1.x related).  "The New ABI" is really the third 
ABI.

>   gcc 3.3.2	new abi, version 1
3.1
>   gcc 3.4.0	new abi, version 2
3.2
> 
> Here's an example of the differences between "new abi, version 1"
> and "new abi, version 2": suppose that a class has a virtual destructor,
> but the user doesn't specify the virtual destructor, so the compiler
> synthesizes it.  With "new abi, version 1", the synthesized virtual
> destructor appears in the vtable *before* the user's own virtual
> methods.  With "new abi, version 2", the synthesized virtual destructor
> appears in the vtable *after* the user's own virtual methods.
> 
> There are about 5-10 tweaks like this in gcc 3.4.
> 
> So it's not "New New ABI", fortunately for us.  It's just bug fixes
> to "New ABI".  It's the same mangling scheme and same data structures,
> but gcc puts slightly different data into them.  Different enough that
> g++ 3.3.X and g++ 3.4.X are sometimes not link-compatible, but similar
> enough that gdb will not need a new module.
> 
> gcc 3.4 has a flag "-fabi-version" to select between "New Abi,
> version 1" and "New Abi, version 2".  "New Abi, version 2" is the
> default.

So "abi-version" is the minor version :-/

"logical" :-^

Andrew