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Re: [PATCH] Diagnose invalid pointer arithmetic on gdb.Value

On 20/09/16 17:42 +0100, Pedro Alves wrote:
On 09/20/2016 05:19 PM, Jonathan Wakely wrote:
On 20/09/16 16:41 +0100, Pedro Alves wrote:
On 09/20/2016 03:46 PM, Jonathan Wakely wrote:
Instead of passing invalid arguments to value_binop and getting a
misleading error, raise a TypeError directly in valpy_binop_throw.

Did you try changing value_binop instead?  The error string seems
misleading even in C:

(gdb) p ptr
$1 = 0x601040 <buf> ""
(gdb) p ptr + 1
$2 = 0x601041 <buf+1> ""
(gdb) p ptr + 1.0
Argument to arithmetic operation not a number or boolean.

Ah, so it's not specific to the Python API, in which case changing
value_binop (or scalar_binop more accurately) might make sense.
The check in scalar_binop *does* check for numbers, so the error is
accurate. The argument that triggers the errors is actually the
pointer argument, not the float one:

 if ((TYPE_CODE (type1) != TYPE_CODE_FLT
      && TYPE_CODE (type1) != TYPE_CODE_DECFLOAT
      && !is_integral_type (type1))
     || (TYPE_CODE (type2) != TYPE_CODE_FLT
      && TYPE_CODE (type2) != TYPE_CODE_DECFLOAT
      && !is_integral_type (type2)))
   error (_("Argument to arithmetic operation not a number or boolean."));

The problem is that pointer arithmetic with invalid operands ends up
here, because value_ptr{add,sub,diff} don't get called for invalid

So maybe a better fix is to first check if either argument is a
pointer and give a more specific error, as attached (untested).

Makes sense to me.

Here's a patch to do that. None of the existing tests needed to change
as far as I can see. gdb.base/pointers.exp and gdb.base/completion.exp
have tests that try to match the old error, but they're commented out.

I kept my additions to py-value.exp that do invalid pointer
arithmetic, updating the expected text. Should I move that to
gdb.base/pointers.exp instead? Or check it in both?

Attachment: pr20622.txt
Description: Text document

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