Re: [PATCH] Clear *VAL in regcache_raw_read_unsigned

[Pedro Alves <palves at redhat dot com>]

On 02/11/2016 03:15 PM, Yao Qi wrote:

> I think this is better than 'make gdbserver use extract_unsigned_integer',
> which looks overkill to me.

I think it's only going to bite us back in the future.

>From the perspective of potentially making it easier to share more
code between gdb and gdbserver, I'd prefer that.  Would you object it?

> 
>>
>> Or maybe better, just byte the bullet and make gdbserver use
>> extract_unsigned_integer, like gdb.
>>
>> The problem with that is that gdbserver can't currently use 'enum bfd_endian',
>> which IIRC, was already an issue in the get-next-pcs stuff.  I've attached a
> 
> get-next-pcs stuff needs endianness in GDB side.  In GDBserver,
> endianness is not needed.

The get-next-pcs stuff does have endianness bits, but it works
around the lack of 'enum bfd_endian' by hacking it through an int instead:

void
arm_get_next_pcs_ctor (struct arm_get_next_pcs *self,
		       struct arm_get_next_pcs_ops *ops,
		       int byte_order,
		       int byte_order_for_code,
		       int has_thumb2_breakpoint,
		       struct regcache *regcache)
{

$ grep byte_order *

arm-get-next-pcs.c:                    int byte_order,
arm-get-next-pcs.c:                    int byte_order_for_code,
arm-get-next-pcs.c:  self->byte_order = byte_order;
arm-get-next-pcs.c:  self->byte_order_for_code = byte_order_for_code;
arm-get-next-pcs.c:  int byte_order_for_code = self->byte_order_for_code;
arm-get-next-pcs.c:  insn1 = self->ops->read_mem_uint (loc, 2, byte_order_for_code);
arm-get-next-pcs.c:  insn2 = self->ops->read_mem_uint (loc, 2, byte_order_for_code);
arm-get-next-pcs.c:      insn1 = self->ops->read_mem_uint (loc, 2,byte_order_for_code);
arm-get-next-pcs.c:       insn2 = self->ops->read_mem_uint (loc, 2, byte_order_for_code);
arm-get-next-pcs.c:  int byte_order_for_code = self->byte_order_for_code;
arm-get-next-pcs.c:  insn = self->ops->read_mem_uint (loc, 4, byte_order_for_code);
arm-get-next-pcs.c:      insn = self->ops->read_mem_uint (loc, 4, byte_order_for_code);
arm-get-next-pcs.c:  int byte_order = self->byte_order;
arm-get-next-pcs.c:  int byte_order_for_code = self->byte_order_for_code;
arm-get-next-pcs.c:  inst1 = self->ops->read_mem_uint (pc, 2, byte_order_for_code);
arm-get-next-pcs.c:           inst1 = self->ops->read_mem_uint (pc, 2,byte_order_for_code);
arm-get-next-pcs.c:               inst1 = self->ops->read_mem_uint (pc, 2, byte_order_for_code);
arm-get-next-pcs.c:               inst1 = self->ops->read_mem_uint (pc, 2, byte_order_for_code);
arm-get-next-pcs.c:      nextpc = self->ops->read_mem_uint (sp + offset, 4, byte_order);
arm-get-next-pcs.c:      inst2 = self->ops->read_mem_uint (pc + 2, 2, byte_order_for_code);
arm-get-next-pcs.c:           nextpc = self->ops->read_mem_uint (addr + offset, 4, byte_order);
arm-get-next-pcs.c:           = self->ops->read_mem_uint (base, 4, byte_order);
arm-get-next-pcs.c:       length = 2 * self->ops->read_mem_uint (table + offset, 1, byte_order);
arm-get-next-pcs.c:       length = 2 * self->ops->read_mem_uint (table + offset, 2, byte_order);
arm-get-next-pcs.c:  int byte_order = self->byte_order;
arm-get-next-pcs.c:  int byte_order_for_code = self->byte_order_for_code;
arm-get-next-pcs.c:  this_instr = self->ops->read_mem_uint (pc, 4, byte_order_for_code);
arm-get-next-pcs.c:                                                         4, byte_order);
arm-get-next-pcs.c:                                                              4, byte_order);
arm-get-next-pcs.h:  ULONGEST (*read_mem_uint) (CORE_ADDR memaddr, int len, int byte_order);
arm-get-next-pcs.h:  int byte_order;
arm-get-next-pcs.h:  int byte_order_for_code;
arm-get-next-pcs.h:                         int byte_order,
arm-get-next-pcs.h:                         int byte_order_for_code,


> 
>> patch series that handles that by moving bfd_endian to a separate header.
>> I've pushed it to the users/palves/gdbserver-extract-unsigned-integer branch
>> as well.
>>
>> If you agree with this, I'll run the bfd_endian patch by the binutils folks.
> 
> Since the endianness of GDBserver is always identical to the endianness
> of the program, I am not sure sharing extract_unsigned_integer between
> GDB and GDBserver is necessary.

Thanks,
Pedro Alves