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Re: [PATCH] DWARFv5 DW_TAG_aligned_type.
- From: Tom Tromey <tromey at redhat dot com>
- To: Mark Wielaard <mjw at redhat dot com>
- Cc: gdb-patches at sourceware dot org, Joel Brobecker <brobecker at adacore dot com>
- Date: Fri, 11 Jul 2014 09:23:45 -0600
- Subject: Re: [PATCH] DWARFv5 DW_TAG_aligned_type.
- Authentication-results: sourceware.org; auth=none
- References: <1404944457-4500-1-git-send-email-mjw at redhat dot 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