uninitialized typedef in value_sub on pointers

[Andrew Cagney]

Kevin Nomura wrote:
> 
> Sometimes the second operand of a pointer subtraction has
> incomplete type info loaded, resulting in a bogus but
> self-repairing error as demonstrated by:
> 
> (gdb)  p (sk_Proc *) fm_givebackPid-sk_proc_table
> First argument of `-' is a pointer and second argument is neither
> an integer nor a pointer of the same type.
> >>> this next line was retrived with the uparrow, and a single space
> >>added at the end, which seems to make a difference:
> (gdb)  p (sk_Proc *) fm_givebackPid-sk_proc_table
> $1 = 0
> 
> Reproduces with gdb 4.18 and gdb 5.0, but not with the small
> testcase I tried to craft.
> 
> I made the following patch to gdb-5.0/valarith.c:value_sub() to
> get around this problem:
> 
> 113,114c113,114
> <              && TYPE_LENGTH (check_typedef (TYPE_TARGET_TYPE (type1)))
> <              == TYPE_LENGTH (check_typedef (TYPE_TARGET_TYPE (type2))))
> ---
> >              && TYPE_LENGTH (TYPE_TARGET_TYPE (type1))
> >              == TYPE_LENGTH (TYPE_TARGET_TYPE (type2)))
> 
> Perhaps someone with more knowledge of the way gdb loads symbol
> info can divine the true nature of this bug and/or whether this
> is an appropriate fix.

Hello,

Would you be able to have another go of creating a test case?  Without
things like the source code, a knowledge of the host/target, debug info
and the like it will be difficult for people to analize this problem.

	Andrew