Re: [RFC] rl78: vtables are code addresses

[Pedro Alves <palves@redhat.com>]

On 02/11/2014 06:44 AM, Kevin Buettner wrote:

> I would like to commit this patch because, on balance, it markedly
> improves the test results.  Without objection(s), I'll commit this
> patch in a few days time.
> 
> Kevin
> 
> 	* rl78-tdep.c (rl78_pointer_to_address): Add logic so that
> 	vtables are considered to be code addresses.

Isn't this going to be needed for all Harvard targets?
Or rather, can't we always consider this to be code for
all targets?

> 
> diff --git a/gdb/rl78-tdep.c b/gdb/rl78-tdep.c
> index c28db4b..d067b43 100644
> --- a/gdb/rl78-tdep.c
> +++ b/gdb/rl78-tdep.c
> @@ -764,14 +764,27 @@ rl78_pointer_to_address (struct gdbarch *gdbarch,
>                           struct type *type, const gdb_byte *buf)
>  {
>    enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
> +  int vtable = 0;
>    CORE_ADDR addr
>      = extract_unsigned_integer (buf, TYPE_LENGTH (type), byte_order);
>  
> +  /* See if it's a vtable.  */
> +  if (TYPE_CODE (type) == TYPE_CODE_PTR)
> +    {
> +      struct type *targ_type = TYPE_TARGET_TYPE (type);
> +       
> +      if (TYPE_CODE (targ_type) == TYPE_CODE_STRUCT
> +          && TYPE_TAG_NAME (targ_type) != NULL
> +	  && strcmp (TYPE_TAG_NAME (targ_type), "gdb_gnu_v3_abi_vtable") == 0)

Hmm.  gdb_gnu_v3_abi_vtable is a type baked by GDB itself.

> +	vtable = 1;
> +    }
> +
>    /* Is it a code address?  */
>    if (TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_FUNC
>        || TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_METHOD
>        || TYPE_CODE_SPACE (TYPE_TARGET_TYPE (type))

and we already check that the target type is code here.  But
the type system didn't know that.  But, shouldn't it?

> -      || TYPE_LENGTH (type) == 4)
> +      || TYPE_LENGTH (type) == 4
> +      || vtable)
>      return rl78_make_instruction_address (addr);
>    else
>      return rl78_make_data_address (addr);
> 

Thus, wouldn't it be a little better to mark the baked in struct
type as code to begin with?

---
 gdb/gnu-v3-abi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gdb/gnu-v3-abi.c b/gdb/gnu-v3-abi.c
index a08dc36..ceccbe5 100644
--- a/gdb/gnu-v3-abi.c
+++ b/gdb/gnu-v3-abi.c
@@ -171,7 +171,7 @@ build_gdb_vtable_type (struct gdbarch *arch)
   TYPE_TAG_NAME (t) = "gdb_gnu_v3_abi_vtable";
   INIT_CPLUS_SPECIFIC (t);

-  return t;
+  return make_type_with_address_space (t, TYPE_INSTANCE_FLAG_CODE_SPACE);
 }


I believe this makes no difference for archs with flat address space.
(testing on x86-64 GNU/Linux shows no changes).

-- 
1.7.11.7