Re: [PATCH] DWARFv5 DW_TAG_aligned_type.

[Tom Tromey <tromey@redhat.com>]

>>>>> "Mark" == Mark Wielaard <mjw@redhat.com> writes:

Mark> This patch is to deal with the corresponding patch to gcc:
Mark> https://gcc.gnu.org/ml/gcc-patches/2014-07/msg00667.html

Thanks Mark.

Mark> Like the DW_TAG_atomic_type patch (sorry, I haven't dealt yet with all
Mark> the comments), this isn't meant to be applied as is (it is currently only
Mark> a proposal for DWARFv5).

Understood.

Mark> +      if (TYPE_USER_ALIGN (domain) != 0)
Mark> +	fprintf_filtered (stream, " _Alignas (%u)", TYPE_USER_ALIGN (domain));

I think the preferred spelling in C++ is "alignas", not "_Alignas".
It would be a bit prettier if this were language-dependent.
What do you think?  It affects a few spots.

Mark> +/* Add the given user alignment to the element type of the array.  GCC
Mark> +   outputs DWARF type qualifiers that apply to an array, not the
Mark> +   element type.  But GDB relies on the array element type to carry
Mark> +   the cv-qualifiers.  This is mimics section 6.7.3, point 9 of the
Mark> +   C11 specification (n1570).  */
Mark> +static struct type *
Mark> +add_array_cv_aligned_type (struct die_info *die, struct dwarf2_cu *cu,
Mark> +			   struct type *base_type, unsigned int user_align)
Mark> +{

gdb rules put a blank line between the comment and the start of the
function.

Mark> +      TYPE_TARGET_TYPE (inner_array) =
Mark> +	copy_type (TYPE_TARGET_TYPE (inner_array));

The "=" goes on the start of the next line.

 
Mark> +static struct type *
Mark> +read_tag_aligned_type (struct die_info *die, struct dwarf2_cu *cu)
Mark> +{

Needs some kind of intro comment.

Mark> +/* Make a '_Alignas'-qualified version of TYPE (if user_align is
Mark> +   stricter than the user alignment of TYPE).  */
Mark> +
Mark> +struct type *
Mark> +make_aligned_type (struct type *type, unsigned int user_align)
Mark> +{
Mark> +  if (user_align > TYPE_USER_ALIGN (type))
Mark> +    return make_qualified_aligned_type (type, TYPE_INSTANCE_FLAGS (type),
Mark> +					user_align, NULL);

Like Joel I am curious about the need for this.

I thought maybe it was just following the (C & C++) language standard.
But would DWARF like this really be emitted by the compiler?
It wasn't clear to me.

Mark> +	int new_user_align = TYPE_USER_ALIGN (type);

Most spots are using unsigned for this.

Occasionally I'm tempted to adopt the C++ style of ubiquitous typedefs
to avoid this kind of mismatch.  But I've never really brought that up,
so I suggest just changing this instance.

Mark> +2014-07-09  Mark Wielaard  <mjw@redhat.com>
Mark> +
Mark> +	* dwarf2.def: Add DW_TAG_aligned_type and DW_AT_alignment.

Not important now, but when it's time to put the patch in, this change
will have to go to gcc-patches for approval & checkin; then pulled over
to the binutils-gdb tree.  It won't require any additional approval on
this side at least.

Tom