On Tue, Mar 10, 2020 at 07:38:17PM -0400, Marek Polacek via Gcc-patches wrote:
> --- a/gcc/cp/decl.c
> +++ b/gcc/cp/decl.c
> @@ -6062,6 +6062,13 @@ reshape_init_array_1 (tree elt_type, tree max_index,
> reshape_iter *d,
> else if (last_nonzero < nelts - 1)
> nelts = last_nonzero + 1;
>
> + /* Sharing a stripped constructor can get in the way of
> + overload resolution. E.g., initializing a class from
> + {{0}} might be invalid while initializing the same class
> + from {{}} might be valid. */
> + if (reuse)
> + new_init = unshare_constructor (new_init);
> +
> vec_safe_truncate (CONSTRUCTOR_ELTS (new_init), nelts);
Isn't it wasteful to first copy perhaps a large constructor (recursively)
and then truncate it to very few elts (zero in this case)?
So, perhaps doing instead:
if (reuse)
{
vec<constructor_elt, va_gc> *v = NULL;
if (nelts)
vec_alloc (v, nelts);
for (unsigned int i = 0; i < nelts; i++)
{
constructor_elt elt = CONSTRUCTOR_ELT (new_init, i);
if (TREE_CODE (elt.value) == CONSTRUCTOR)
elt.value = unshare_constructor (elt.value);
v->quick_push (elt);
}
new_init = build_constructor (TREE_TYPE (new_init), v);
}
else
vec_safe_truncate (CONSTRUCTOR_ELTS (new_init), nelts);
?
Jakub
