https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88140
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jsm28 at gcc dot gnu.org
--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
Hmm, no. But somehow re-building the array type yields TYPE_SIZE == NULL_TREE
rather than TYPE_SIZE == integer_zero_node.
That happens in
Old value = <tree 0x0>
New value = <integer_cst 0x7ffff687ad08>
grokdeclarator (declarator=0x3028700, declspecs=0x30285a0, decl_context=FIELD,
initialized=false, width=0x0, decl_attrs=0x7fffffffd518,
expr=0x7fffffffd2d0, expr_const_operands=0x7fffffffd2cf,
deprecated_state=DEPRECATED_NORMAL)
at /space/rguenther/src/gcc-sccvn/gcc/c/c-decl.c:6397
6397 TYPE_SIZE_UNIT (type) = size_zero_node;
/* The GCC extension for zero-length arrays differs from
ISO flexible array members in that sizeof yields
zero. */
if (size && integer_zerop (size))
{
gcc_assert (itype);
type = build_distinct_type_copy (TYPE_MAIN_VARIANT (type));
TYPE_SIZE (type) = bitsize_zero_node;
TYPE_SIZE_UNIT (type) = size_zero_node;
SET_TYPE_STRUCTURAL_EQUALITY (type);
}
and this overrides what layout_type does.
The cleanest fix would be to add a type flag ARRAY_TYPE_ZERO_LENGTH but then
the odd thing is that adjusting the domain to be [0, -1] instead of [0, ]
would probably make layout_type do the same decision?!
For the free-lang-data regression the following is a simple fix which I am
testing now:
diff --git a/gcc/tree.c b/gcc/tree.c
index 39a92464414..a39e611292a 100644
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -5201,6 +5201,15 @@ fld_process_array_type (tree t, tree t2, hash_map<tree,
tree> *map,
array = build_array_type_1 (t2, TYPE_DOMAIN (t),
TYPE_TYPELESS_STORAGE (t), false);
TYPE_CANONICAL (array) = TYPE_CANONICAL (t);
+ /* Re-building the array via build_array_type_1 causes the C FE
+ special-handling of zero-length arrays to be dropped. So
+ we copy back TYPE_SIZE[_UNIT] from the original type here
+ if layout_type decided the type is incomplete. */
+ if (!TYPE_SIZE (array))
+ {
+ TYPE_SIZE (array) = TYPE_SIZE (t);
+ TYPE_SIZE_UNIT (array) = TYPE_SIZE_UNIT (t);
+ }
add_tree_to_fld_list (array, fld);
}
return array;
