On Tue, 19 Sep 2017, Nathan Sidwell wrote:
> > > > After recent changes, the member_name_cmp qsort comparator can indicate
> > > > A < B < A (i.e. lacks anti-commutativity) for distinct TYPE_DECL nodes
> > > > that have the same source location. If their order doesn't matter, the
> > > > comparator should return 0.
> > >
> > > Where do we get such type decls?
> >
> > The first instance that tripped qsort checking for me was in PCH generation.
> > I think by adding
>
> What source example generates such type decls? That you've encountered this
> suggests one of the invariants I was presuming is not true.
You can use the gcc_assert mentioned in the previous email on GCC
bootstrap/regtest to find examples. For me, the following example breaks (no
command line flags needed, just bare 'cc1plus t.i'):
struct
{
int a, b, c, d;
union
{
int e;
};
} s;
1436 gcc_assert (DECL_SOURCE_LOCATION (a) != DECL_SOURCE_LOCATION (b));
(gdb) call debug_tree(a)
<type_decl 0x7ffff19f68e8 ._1
type <union_type 0x7ffff19f77e0 ._1 type_5 SI
size <integer_cst 0x7ffff18c0120 constant 32>
unit-size <integer_cst 0x7ffff18c0138 constant 4>
align:32 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type
0x7ffff19f7348
fields <field_decl 0x7ffff19f6980 e type <integer_type 0x7ffff18bd5e8
int>
nonlocal decl_3 SI t.i:6:11 size <integer_cst 0x7ffff18c0120 32>
unit-size <integer_cst 0x7ffff18c0138 4>
align:32 warn_if_not_align:0 offset_align 128
offset <integer_cst 0x7ffff18a0f00 constant 0>
bit-offset <integer_cst 0x7ffff18a0f48 constant 0> context
<union_type 0x7ffff19f7348 ._1> chain <type_decl 0x7ffff19f68e8 ._1>> context
<record_type 0x7ffff19f7f18 ._0>
full-name "union<unnamed struct>::<unnamed>"
chain <type_decl 0x7ffff19f6850 ._1>>
nonlocal decl_4 VOID t.i:5:5
align:1 warn_if_not_align:0 context <union_type 0x7ffff19f7348 ._1>
result <union_type 0x7ffff19f7348 ._1 type_5 SI size <integer_cst
0x7ffff18c0120 32> unit-size <integer_cst 0x7ffff18c0138 4>
align:32 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type
0x7ffff19f7348 fields <field_decl 0x7ffff19f6980 e> context <record_type
0x7ffff19f7f18 ._0>
full-name "union<unnamed struct>::<unnamed>"
chain <type_decl 0x7ffff19f6850 ._1>>
>
$1 = 10
(gdb) call debug_tree(b)
<type_decl 0x7ffff19f6850 ._1
type <union_type 0x7ffff19f7348 ._1 type_5 SI
size <integer_cst 0x7ffff18c0120 constant 32>
unit-size <integer_cst 0x7ffff18c0138 constant 4>
align:32 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type
0x7ffff19f7348
fields <field_decl 0x7ffff19f6980 e type <integer_type 0x7ffff18bd5e8
int>
nonlocal decl_3 SI t.i:6:11 size <integer_cst 0x7ffff18c0120 32>
unit-size <integer_cst 0x7ffff18c0138 4>
align:32 warn_if_not_align:0 offset_align 128
offset <integer_cst 0x7ffff18a0f00 constant 0>
bit-offset <integer_cst 0x7ffff18a0f48 constant 0> context
<union_type 0x7ffff19f7348 ._1> chain <type_decl 0x7ffff19f68e8 ._1>> context
<record_type 0x7ffff19f7f18 ._0>
full-name "union<unnamed struct>::<unnamed>"
chain <type_decl 0x7ffff19f6850 ._1>>
decl_2 decl_5 VOID t.i:5:5
align:8 warn_if_not_align:0 context <record_type 0x7ffff19f7f18 ._0>>
$2 = 10
