Re: [PATCH 2/2] arm-tdep.c: Refactor displaced stepping relocation functions

Luis Machado
2016-02-26T16:50:36Z

On 02/26/2016 01:23 PM, Simon Marchi wrote:
>>> diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c
>>> index 43b61c2..ef48a90 100644
>>> --- a/gdb/arm-tdep.c
>>> +++ b/gdb/arm-tdep.c
>>> @@ -7111,9 +7111,8 @@ thumb_copy_pop_pc_16bit (uint16_t insn1, struct arm_insn_reloc_data *data)
>>> return 0;
>>> }
>>>
>>> -static void
>>> -thumb_process_displaced_16bit_insn (uint16_t insn1,
>>> - struct arm_insn_reloc_data *data)
>>> +static int
>>> +arm_relocate_insn_thumb_16bit (uint16_t insn1, struct arm_insn_reloc_data *data)
>>> {
>>> unsigned short op_bit_12_15 = bits (insn1, 12, 15);
>>> unsigned short op_bit_10_11 = bits (insn1, 10, 11);
>>> @@ -7202,9 +7201,7 @@ thumb_process_displaced_16bit_insn (uint16_t insn1,
>>> err = 1;
>>> }
>>>
>>> - if (err)
>>> - internal_error (__FILE__, __LINE__,
>>> - _("thumb_process_displaced_16bit_insn: Instruction decode error"));
>>> + return err;
>>
>> Should we keep this internal error message under a different context
>> instead of exporting just an error code? Maybe the error code should
>> trigger this internal error for GDB?
>
> I am not sure I understand your comment. Given this call tree:
>
> - arm_process_displaced_insn
> - arm_relocate_insn_arm
> ...
> - arm_relocate_insn_thumb_32bit
> ...
> - arm_relocate_insn_thumb_16bit
> ...
>
> my patch makes it so that the arm_relocate_insn* functions return an error code, and
> arm_process_displaced_insn calls internal_error if an error is returned. Do you suggest
> putting the internal_error calls in the arm_relocate_insn_* functions directly?
>

No. If we want them shared, i don't think we'd want them to throw
internal errors.

I was just pointing out the fact that we're losing the function name
information from arm_relocate_insn_thumb_16bit's and
thumb_process_displaced_32bit_insn's internal error messages. This
information may make debugging easier. We would need to throw errors
with custom messages from within arm_process_displaced_insn in order to
maintain those names. For example:

"thumb_process_displaced_16bit_insn: Instruction decode error"
"thumb_process_displaced_32bit_insn: Instruction decode error"

Instead of:

"arm_process_displaced_insn: Instruction decode error"

I see the regular non-thumb functions don't throw internal errors
themselves though. So i'm fine if others think the more specific error
message is not needed.

Luis