Helping out GDB

[Martin v. Loewis]

> > Why is that? If the symbols start with __vt_, it's vtable thunks; if
> > they start with __vt., it's old-style vtables. Is that difficult to
> > tell apart? 
> 
> Last time I looked, whether "." was a valid character for an object format 
> was a back-end choice (the assembler may not grok it).  In such cases, 
> either "$" or, in the worst case, "_" is substituted instead.  So in 
> general: No, it isn't enough.

There are three possibilites:
                     thunks         nothunks
$ in label           __vt_          _vt$
. in label           __vt_          _vt.
neither/nor          __vt_          _vt_

So it's actually the "__vt" prefix that allows to reliably tell apart
thunks vs nothunks.

Regards,
Martin