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Re: C++ related core dump
- From: Daniel Jacobowitz <drow at false dot org>
- To: Mark Kettenis <kettenis at jive dot nl>
- Cc: gdb at sourceware dot org
- Date: Wed, 16 Nov 2005 23:10:56 -0500
- Subject: Re: C++ related core dump
- References: <200511151015.jAFAFKXw032226@jop31.nfra.nl>
On Tue, Nov 15, 2005 at 11:15:20AM +0100, Mark Kettenis wrote:
> I'm debugging some evil C++ code at work, and gdb keeps dumping core
> on me:
>
> (gdb) ptype antennac
> type = class ROScalarColumn<int> : public virtual ROTableColumn {
...
> Int operator()(unsigned int) const;
> (gdb) p antennac(0)
> Segmentation fault (core dumped)
>
> This is with gcc 3.2 on sparc-sun-solaris2.7, which still uses stabs
> debugging info.
>
> I tracked it down to some code in valops.c:find_overload_match(),
> where SYMBOL_CPLUS_DEMANGLED_NAME is returning a null pointer which we
> pass to cp_func_name() and that function can't deal with that. As a
> stopgap, I applied the attached patch, and now I get:
>
> (gdb) p antennac(0)
> Invalid data type for function to be called.
>
> which isn't quite what I want, but at least keeps my gdb alive.
>
> What I really want of course is for the above to invoke
> antennac.operator()(0). Is that supposed to work at all? I know
> stabs support for C++ has issues, but reading the code I don't see how
> this would work for DWARF2 either.
Well certainly that's not going to work :-) antennac(0) is not an
invocation of operator(). It's an invocation of the antennac class
constructor. If you want to invoke operator(), you need an object.
If you had an object, I would expect this to work (or mostly work); GDB
does support user-defined operators.
GDB does _not_ support calling constructors, though. This is a bit
tricky.
> Regardless of properly invoking operator(), we should do something
> about this crash. Can we do something better than the attached patch?
> - func_name = cp_func_name (qualified_name);
> + if (qualified_name)
> + func_name = cp_func_name (qualified_name);
Return earlier if fsym is not a function? Or this seems reasonable, to
avoid the crash.
--
Daniel Jacobowitz
CodeSourcery, LLC