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Re: Problem with virtual function pointers
On Thu, Mar 27, 2003 at 04:20:22PM +0100, Corinna Vinschen wrote:
> On Thu, Mar 27, 2003 at 09:53:46AM -0500, Daniel Jacobowitz wrote:
> > On Thu, Mar 27, 2003 at 03:24:12PM +0100, Corinna Vinschen wrote:
> > > Hi,
> > >
> > > I'm just investigating a problem which XStormy16 gets in
> > > gdb.c++/printmethod.exp:
> > >
> > > print theA->virt^M
> > > $1 = invalid pointer to member function^M
> > > FAIL: gdb.c++/printmethod.exp: print virtual method.
> > >
> > > It turned out that the error happens in xstormy16_pointer_to_address().
> > > This function converts an address to a jump table entry into a pointer
> > > to the actual function. To do this, it calls a conversion routine,
> > > which is only called if the following condition applies:
> > >
> > >
> > > enum type_code target = TYPE_CODE (TYPE_TARGET_TYPE (type));
> > >
> > > if (target == TYPE_CODE_FUNC || target == TYPE_CODE_METHOD)
> > > convert();
> > >
> > > Surprisingly (at least for me) this fails for the above case. Looking
> > > into type, I found that type is TYPE_CODE_PTR which is correct, but
> > > target_type is TYPE_CODE_VOID! Sure, the above virtual method is of
> > > type void but is that really ok? Shouldn't that be
> > >
> > > type: TYPE_CODE_PTR
> > > type->target_type: TYPE_CODE_METHOD
> > > type->target_type->target_type: TYPE_CODE_VOID
> > >
> > > ?
> >
> > Could you give me a backtrace?
>
> Sure. The situation is after calling `print theA->virt' and stepping
> into xstormy16_pointer_to_address().
>
> (top-gdb) bt
> #0 xstormy16_pointer_to_address (type=0x848d628, buf=0x85f4348)
> at /home/corinna/src/gdb/xstormy16-tdep.c:966
> #1 0x080fa69e in gdbarch_pointer_to_address (gdbarch=0x848ac90,
> type=0x848d628, buf=0x85f4348)
> at /home/corinna/src/gdb/gdbarch.c:4164
> #2 0x080b3219 in extract_typed_address (buf=0x85f4348, type=0x848d628)
> at /home/corinna/src/gdb/findvar.c:197
> #3 0x080bc1a3 in unpack_long (type=0x848d628, valaddr=0x85f4348 ":®")
> at /home/corinna/src/gdb/values.c:696
> #4 0x080bc2a6 in unpack_pointer (type=0x848d628, valaddr=0x85f4348 ":®")
> at /home/corinna/src/gdb/values.c:775
> #5 0x0813876e in cp_print_class_method (valaddr=0x85f4348 ":®",
> type=0x84aa064, stream=0x8490f08)
> at /home/corinna/src/gdb/cp-valprint.c:90
There's your bug, right on schedule. Look at the line:
addr = unpack_pointer (lookup_pointer_type (builtin_type_void), valaddr);
Recommend using builtin_type_void_func_ptr instead of
lookup_pointer_type (builtin_type_void). Does that fix it?
--
Daniel Jacobowitz
MontaVista Software Debian GNU/Linux Developer