假设我有一个菱形层次结构,如下面的代码所示。
class A {
public:
A() {}
int a = 3;
virtual void aa() {}
};
class B : public virtual A {
public:
B() : A() {}
int b() { return 4; };
};
class C : public virtual A {
public:
C() : A() {}
};
class D : public B, public C {
protected:
int d = 45;
public:
D() : B(), C() {}
};
我有一个这样的主要:
int main() {
std::unique_ptr<A> a = std::make_unique<D>();
}
以上主要导致段错误。但是添加
a.release()
to main 解决了段错误。这是为什么?
最佳答案
这是因为 A 中没有虚拟 Dtor。没有 Dtor,您可以看到在使用 GDB 运行时对象销毁中发生了段错误:
eddy@eddy-VirtualBox:~/deleteme$ g++ -std=c++14 -O0 -g test.cpp
eddy@eddy-VirtualBox:~/deleteme$ gdb a.out
(gdb) run
Starting program: /home/eddy/deleteme/a.out
Program received signal SIGSEGV, Segmentation fault.
0x00007ffff76f2c01 in __GI___libc_free (mem=0x555555769e88) at malloc.c:3123
3123 malloc.c: No such file or directory.
(gdb) bt
#0 0x00007ffff76f2c01 in __GI___libc_free (mem=0x555555769e88) at malloc.c:3123
#1 0x0000555555554f6d in std::default_delete<A>::operator() (this=0x7fffffffddd8, __ptr=0x555555769e88) at /usr/include/c++/7/bits/unique_ptr.h:78
#2 0x0000555555554e07 in std::unique_ptr<A, std::default_delete<A> >::~unique_ptr (this=0x7fffffffddd8, __in_chrg=<optimized out>)
at /usr/include/c++/7/bits/unique_ptr.h:268
#3 0x0000555555554b68 in main () at test.cpp:33
向 A 类添加虚拟析构函数可以解决此问题:
public:
A() {}
int a = 3;
virtual void aa() {}
virtual ~A() = default;
};
关于c++ - 钻石物体的定义,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/60950126/