Fix scoped enum debug info (PR debug/58150)

Hi!

As the following testcase shows, we emit bad debug info if a scoped
enum is used before the enumerators are defined.
gen_enumeration_type_die has support for enum forward declarations that
have NULL TYPE_SIZE (i.e. incomplete), but in this case it is complete,
just is ENUM_IS_OPAQUE and the enumerators aren't there.  We still set
TREE_ASM_WRITTEN on it and therefore don't do anything when it actually is
completed.

The following patch does change/fix a bunch of things:
1) I don't see the point of guarding the addition of DW_AT_declaration
to just -gdwarf-4 or -gno-strict-dwarf, that is already DWARF2 attribute and
we are emitting it for the forward declarations already
2) we don't set TREE_ASM_WRITTEN if ENUM_IS_OPAQUE
3) we don't try to do anything if it is ENUM_IS_OPAQUE that hasn't been
newly created; similarly to incomplete forward redeclarations, we should
have provided all that is needed on the first declaration
4) the addition of most attributes guarded with TYPE_SIZE is guarded by
(!original_type_die || !get_AT (type_die, DW_AT_...)); the
!original_type_die || part is just an optimization, so we don't try to query
it in the common cases where we are creating a fresh type die; anyway, the
reason for the guards is that we can now do the code twice for the same
type_die (on declaration and definition), and don't want to add the attributes
twice
5) not sure if ENUM_IS_OPAQUE must always imply non-NULL TYPE_SIZE, if not,
in that case we'd add the DW_AT_deprecated attribute twice

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2018-03-09  Jakub Jelinek  <jakub@redhat.com>

	PR debug/58150
	* dwarf2out.c (gen_enumeration_type_die): Don't guard adding
	DW_AT_declaration for ENUM_IS_OPAQUE on -gdwarf-4 or -gno-strict-dwarf,
	but on TYPE_SIZE.  Don't do anything for ENUM_IS_OPAQUE if not creating
	a new die.  Don't set TREE_ASM_WRITTEN if ENUM_IS_OPAQUE.  Guard
	addition of most attributes on !orig_type_die or the attribute not
	being present already.  Assert TYPE_VALUES is NULL for ENUM_IS_OPAQUE.

	* g++.dg/debug/dwarf2/enum2.C: New test.


	Jakub

OK.

On Fri, Mar 9, 2018 at 1:15 PM, Jakub Jelinek <jakub@redhat.com> wrote:
> Hi!
>
> As the following testcase shows, we emit bad debug info if a scoped
> enum is used before the enumerators are defined.
> gen_enumeration_type_die has support for enum forward declarations that
> have NULL TYPE_SIZE (i.e. incomplete), but in this case it is complete,
> just is ENUM_IS_OPAQUE and the enumerators aren't there.  We still set
> TREE_ASM_WRITTEN on it and therefore don't do anything when it actually is
> completed.
>
> The following patch does change/fix a bunch of things:
> 1) I don't see the point of guarding the addition of DW_AT_declaration
> to just -gdwarf-4 or -gno-strict-dwarf, that is already DWARF2 attribute and
> we are emitting it for the forward declarations already
> 2) we don't set TREE_ASM_WRITTEN if ENUM_IS_OPAQUE
> 3) we don't try to do anything if it is ENUM_IS_OPAQUE that hasn't been
> newly created; similarly to incomplete forward redeclarations, we should
> have provided all that is needed on the first declaration
> 4) the addition of most attributes guarded with TYPE_SIZE is guarded by
> (!original_type_die || !get_AT (type_die, DW_AT_...)); the
> !original_type_die || part is just an optimization, so we don't try to query
> it in the common cases where we are creating a fresh type die; anyway, the
> reason for the guards is that we can now do the code twice for the same
> type_die (on declaration and definition), and don't want to add the attributes
> twice
> 5) not sure if ENUM_IS_OPAQUE must always imply non-NULL TYPE_SIZE, if not,
> in that case we'd add the DW_AT_deprecated attribute twice
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> 2018-03-09  Jakub Jelinek  <jakub@redhat.com>
>
>         PR debug/58150
>         * dwarf2out.c (gen_enumeration_type_die): Don't guard adding
>         DW_AT_declaration for ENUM_IS_OPAQUE on -gdwarf-4 or -gno-strict-dwarf,
>         but on TYPE_SIZE.  Don't do anything for ENUM_IS_OPAQUE if not creating
>         a new die.  Don't set TREE_ASM_WRITTEN if ENUM_IS_OPAQUE.  Guard
>         addition of most attributes on !orig_type_die or the attribute not
>         being present already.  Assert TYPE_VALUES is NULL for ENUM_IS_OPAQUE.
>
>         * g++.dg/debug/dwarf2/enum2.C: New test.
>
> --- gcc/dwarf2out.c.jj  2018-03-08 22:49:41.965225512 +0100
> +++ gcc/dwarf2out.c     2018-03-09 14:53:15.596115625 +0100
> @@ -21839,6 +21839,7 @@ static dw_die_ref
>  gen_enumeration_type_die (tree type, dw_die_ref context_die)
>  {
>    dw_die_ref type_die = lookup_type_die (type);
> +  dw_die_ref orig_type_die = type_die;
>
>    if (type_die == NULL)
>      {
> @@ -21846,20 +21847,18 @@ gen_enumeration_type_die (tree type, dw_
>                           scope_die_for (type, context_die), type);
>        equate_type_number_to_die (type, type_die);
>        add_name_attribute (type_die, type_tag (type));
> -      if (dwarf_version >= 4 || !dwarf_strict)
> -       {
> -         if (ENUM_IS_SCOPED (type))
> -           add_AT_flag (type_die, DW_AT_enum_class, 1);
> -         if (ENUM_IS_OPAQUE (type))
> -           add_AT_flag (type_die, DW_AT_declaration, 1);
> -       }
> +      if ((dwarf_version >= 4 || !dwarf_strict)
> +         && ENUM_IS_SCOPED (type))
> +       add_AT_flag (type_die, DW_AT_enum_class, 1);
> +      if (ENUM_IS_OPAQUE (type) && TYPE_SIZE (type))
> +       add_AT_flag (type_die, DW_AT_declaration, 1);
>        if (!dwarf_strict)
>         add_AT_unsigned (type_die, DW_AT_encoding,
>                          TYPE_UNSIGNED (type)
>                          ? DW_ATE_unsigned
>                          : DW_ATE_signed);
>      }
> -  else if (! TYPE_SIZE (type))
> +  else if (! TYPE_SIZE (type) || ENUM_IS_OPAQUE (type))
>      return type_die;
>    else
>      remove_AT (type_die, DW_AT_declaration);
> @@ -21871,10 +21870,14 @@ gen_enumeration_type_die (tree type, dw_
>      {
>        tree link;
>
> -      TREE_ASM_WRITTEN (type) = 1;
> -      add_byte_size_attribute (type_die, type);
> -      add_alignment_attribute (type_die, type);
> -      if (dwarf_version >= 3 || !dwarf_strict)
> +      if (!ENUM_IS_OPAQUE (type))
> +       TREE_ASM_WRITTEN (type) = 1;
> +      if (!orig_type_die || !get_AT (type_die, DW_AT_byte_size))
> +       add_byte_size_attribute (type_die, type);
> +      if (!orig_type_die || !get_AT (type_die, DW_AT_alignment))
> +       add_alignment_attribute (type_die, type);
> +      if ((dwarf_version >= 3 || !dwarf_strict)
> +         && (!orig_type_die || !get_AT (type_die, DW_AT_type)))
>         {
>           tree underlying = lang_hooks.types.enum_underlying_base_type (type);
>           add_type_attribute (type_die, underlying, TYPE_UNQUALIFIED, false,
> @@ -21882,8 +21885,10 @@ gen_enumeration_type_die (tree type, dw_
>         }
>        if (TYPE_STUB_DECL (type) != NULL_TREE)
>         {
> -         add_src_coords_attributes (type_die, TYPE_STUB_DECL (type));
> -         add_accessibility_attribute (type_die, TYPE_STUB_DECL (type));
> +         if (!orig_type_die || !get_AT (type_die, DW_AT_decl_file))
> +           add_src_coords_attributes (type_die, TYPE_STUB_DECL (type));
> +         if (!orig_type_die || !get_AT (type_die, DW_AT_accessibility))
> +           add_accessibility_attribute (type_die, TYPE_STUB_DECL (type));
>         }
>
>        /* If the first reference to this type was as the return type of an
> @@ -21897,6 +21902,7 @@ gen_enumeration_type_die (tree type, dw_
>           dw_die_ref enum_die = new_die (DW_TAG_enumerator, type_die, link);
>           tree value = TREE_VALUE (link);
>
> +         gcc_assert (!ENUM_IS_OPAQUE (type));
>           add_name_attribute (enum_die,
>                               IDENTIFIER_POINTER (TREE_PURPOSE (link)));
>
> @@ -21926,7 +21932,8 @@ gen_enumeration_type_die (tree type, dw_
>         }
>
>        add_gnat_descriptive_type_attribute (type_die, type, context_die);
> -      if (TYPE_ARTIFICIAL (type))
> +      if (TYPE_ARTIFICIAL (type)
> +         && (!orig_type_die || !get_AT (type_die, DW_AT_artificial)))
>         add_AT_flag (type_die, DW_AT_artificial, 1);
>      }
>    else
> --- gcc/testsuite/g++.dg/debug/dwarf2/enum2.C.jj        2018-03-09 15:14:44.982388983 +0100
> +++ gcc/testsuite/g++.dg/debug/dwarf2/enum2.C   2018-03-09 15:14:28.449385285 +0100
> @@ -0,0 +1,30 @@
> +// PR debug/58150
> +// { dg-do compile }
> +// { dg-options "-std=c++11 -gdwarf-4 -dA -fno-merge-debug-strings" }
> +// { dg-final { scan-assembler-times "DIE\[^\n\r\]*DW_TAG_enumeration_type" 3 } }
> +// { dg-final { scan-assembler-times " DW_AT_enum_class" 3 } }
> +// { dg-final { scan-assembler-times " DW_AT_declaration" 1 } }
> +// { dg-final { scan-assembler-times "\"E1..\"\[^\n\]*DW_AT_name" 1 } }
> +// { dg-final { scan-assembler-times "\"E2..\"\[^\n\]*DW_AT_name" 1 } }
> +// { dg-final { scan-assembler-times "\"F1..\"\[^\n\]*DW_AT_name" 1 } }
> +// { dg-final { scan-assembler-times "\"F2..\"\[^\n\]*DW_AT_name" 1 } }
> +
> +enum class E : int;
> +enum class F : int;
> +enum class G : int;
> +struct S { E s; };
> +struct T { G t; };
> +enum class E : int
> +{
> +  E1, E2
> +};
> +enum class F : int
> +{
> +  F1, F2
> +};
> +
> +bool
> +foo (E e, F f, G g)
> +{
> +  return e == E::E1 && f == F::F1 && (int) g == 0;
> +}
>
>         Jakub