has_unique_object_representations和空子对象不一致

问题描述

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？

解决方法

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