OK.
On Thu, Jan 19, 2017 at 10:32 AM, Jakub Jelinek <ja...@redhat.com> wrote:
> Hi!
>
> This is on top of the PR78835 patch I've posted yesterday.
> We ICE on the following testcase reduced from libstdc++ ios_failure.cc.
> If there are nested comdat types, as B (outer type) and A (inner type) in the
> testcase, we first move A to a type unit and add there copies of its
> children, and preserve a skeleton copy of A in the main CU with the
> originals of their children (i.e. something other DIEs may refer to).
> Then we try to move B into another type unit, but mishandle the children,
> the DIE for foo subprogram ends up in the B type unit rather than in the
> main CU where it belongs. Of course nothing can refer to that there from
> outside of that type unit.
>
> Either hunk in dwarf2out.c is actually enough to fix the ICE. The second
> hunk fixes the bug that after the moving of the children etc. we end up with
> node.old_die == node.new_die, which is obviously wrong. We always want
> old_die to be the DIE that will be in the type unit while new_die one that
> will remain in the main CU. The first hunk is an optimization, my
> understanding is that the creation of the skeleton DIEs is so that uses
> outside of the type unit (i.e. from the main CU) can actually refer to those
> DIEs (when we lookup_decl_die etc.; from main CU to type units we can only
> refer using DW_FORM_ref_sig8 to the type unit's single chosen type die).
> As break_out_comdat_types and its helpers don't actually adjust random
> references, for nested types I actually think it is enough to have in the
> type unit of the outer type just a skeleton unit of the inner type with
> DW_AT_signature of the type residing in yet another type unit, I think there
> is no way to refer to its children from that type unit. So there is no need
> to duplicate the children and we can just move them to the main CU.
>
> Bootstrapped/regtested on i686-linux with -fdebug-types-section hacked in
> common.opt to be the default, ok for trunk?
>
> Note Ada bootstrap on x86_64-linux with -fdebug-types-section is still
> broken, but that is preexisting, not introduced by this patch:
> .../gcc/gnat1 -gnatwa -quiet -nostdinc -dumpbase g-pehage.adb -auxbase-strip
> g-pehage.o -O2 -Wextra -Wall -g -fpic -gnatpg -mtune=generic -march=x86-64
> -gnatO g-pehage.o g-pehage.adb -o /tmp/ccrAYuNB.s -fdebug-types-section
> raised STORAGE_ERROR : stack overflow or erroneous memory access
>
> 2017-01-19 Jakub Jelinek <ja...@redhat.com>
>
> PR debug/79129
> * dwarf2out.c (generate_skeleton_bottom_up): For children with
> comdat_type_p set, just clone them, but keep the children in the
> original DIE.
>
> * g++.dg/debug/dwarf2/pr79129.C: New test.
>
> --- gcc/dwarf2out.c.jj 2017-01-18 13:40:09.000000000 +0100
> +++ gcc/dwarf2out.c 2017-01-19 10:46:36.297776725 +0100
> @@ -7918,6 +7918,19 @@ generate_skeleton_bottom_up (skeleton_ch
> add_child_die (parent->new_die, c);
> c = prev;
> }
> + else if (c->comdat_type_p)
> + {
> + /* This is the skeleton of earlier break_out_comdat_types
> + type. Clone the existing DIE, but keep the children
> + under the original (which is in the main CU). */
> + dw_die_ref clone = clone_die (c);
> +
> + replace_child (c, clone, prev);
> + generate_skeleton_ancestor_tree (parent);
> + add_child_die (parent->new_die, c);
> + c = clone;
> + continue;
> + }
> else
> {
> /* Clone the existing DIE, move the original to the skeleton
> @@ -7936,6 +7949,7 @@ generate_skeleton_bottom_up (skeleton_ch
> replace_child (c, clone, prev);
> generate_skeleton_ancestor_tree (parent);
> add_child_die (parent->new_die, c);
> + node.old_die = clone;
> node.new_die = c;
> c = clone;
> }
> --- gcc/testsuite/g++.dg/debug/dwarf2/pr79129.C.jj 2017-01-19
> 11:15:01.876727938 +0100
> +++ gcc/testsuite/g++.dg/debug/dwarf2/pr79129.C 2017-01-19 11:14:25.000000000
> +0100
> @@ -0,0 +1,12 @@
> +/* PR debug/79129 */
> +/* { dg-do compile } */
> +/* { dg-options "-gdwarf-4 -O2 -fdebug-types-section" } */
> +
> +struct B
> +{
> + struct A { void foo (int &); };
> + A *bar ();
> + ~B () { int a = 1; bar ()->foo (a); }
> +};
> +struct C { ~C (); B c; };
> +C::~C () {}
>
> Jakub
