如何解决has_unique_object_representations和空子对象不一致
我一直在研究C ++ 20的[[no_unique_address]]
属性,并在将其与has_unique_object_representations
类型特征一起使用时发现了一些有趣的行为:
# Gather the data out of the row
#
this_user_id = row['author']
author = row['retweet_of']
followers = row['followers']
age = row['age']
rtfollowers = row['rtfollowers']
rtage = row['rtage']
#
# Is the sender of this tweet in our network?
#
if not this_user_id in G:
G.add_node(this_user_id,attr_dict={
'followers': row['followers'],'age': row['age'],})
#
# If this is a retweet,is the original author a node?
#
if author != "" and not author in G:
G.add_node(author,attr_dict={
'followers': row['rtfollowers'],'age': row['rtage'],add an edge between the two nodes.
#
if author != "":
if G.has_edge(author,this_user_id):
G[author][this_user_id]['weight'] += 1
else:
G.add_weighted_edges_from([(author,this_user_id,1.0)])
nx.write_gexf(G,'tweets1.gexf')
只有最后一个断言对于GCC(干线)和Clang(干线)都失败。据我所知,#include <type_traits>
struct Empty {};
struct A : public Empty {
int x;
};
struct B {
[[no_unique_address]] Empty e;
int x;
};
static_assert (sizeof(A) == sizeof(int));
static_assert (sizeof(B) == sizeof(int));
static_assert(std::has_unique_object_representations_v<A>);
static_assert(std::has_unique_object_representations_v<B>);
和A
在这里的行为没有理由。
这是编译器错误还是有这种差异的原因?
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