On 06/10/16 22:17 +0200, François Dumont wrote:
Another approach is to rely on existing compiler ability to compute
conditional noexcept when defaulting implementations. This is what I
have done in this patch.
The new default constructor on _Rb_tree_node_base is not a problem as
it is not used to build _Rb_tree_node.
Why not?
I'll try to do the same for copy constructor/assignment and move
constructor/assignment.
We need to make sure we don't change whether any of those operations
are trivial (which shouldn't be a problem for copy/move, because they
are definitely very non-trivial and will stay that way!)
Does this change the default constructors from non-trivial to trivial?
--- a/libstdc++-v3/include/bits/stl_tree.h
+++ b/libstdc++-v3/include/bits/stl_tree.h
@@ -108,6 +108,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_Base_ptr _M_left;
_Base_ptr _M_right;
+ _Rb_tree_node_base() _GLIBCXX_NOEXCEPT
+ : _M_color(_S_red), _M_parent(0), _M_left(this), _M_right(this)
+ { }
+
static _Base_ptr
_S_minimum(_Base_ptr __x) _GLIBCXX_NOEXCEPT
{
Another option would be:
struct _Head_node : _Rb_tree_node_base {
_Head_node() {
_M_color = _S_red;
_M_parent = _Base_ptr();
_M_left = _M_right = this;
}
};
@@ -603,23 +607,33 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{
_Key_compare _M_key_compare;
_Rb_tree_node_base _M_header;
_Head_node _M_header;
That way *only* this node gets the zero-initialization, not all node
bases.
With either solution we can get rid of _M_header() in every
ctor-initializer-list.
+#if __cplusplus < 201103L
size_type _M_node_count; // Keeps track of size of tree.
+#else
+ size_type _M_node_count = 0; // Keeps track of size of
tree.
+#endif
+#if __cplusplus < 201103L
_Rb_tree_impl()
: _Node_allocator(), _M_key_compare(), _M_header(),
_M_node_count(0)
- { _M_initialize(); }
+ { }
+#else
+ _Rb_tree_impl() = default;
+#endif
_Rb_tree_impl(const _Key_compare& __comp, const _Node_allocator& __a)
- : _Node_allocator(__a), _M_key_compare(__comp), _M_header(),
- _M_node_count(0)
- { _M_initialize(); }
+ : _Node_allocator(__a), _M_key_compare(__comp), _M_header()
+#if __cplusplus < 201103L
+ , _M_node_count(0)
+#endif
Doing this conditionally seems pointless, why not just set it here
unconditionally?
