使用动态内存来避免引用失效

Question

#include <iostream>
#include <vector>
#include <cstring>

using namespace std; //please ignore bad practices like this and everything being set to public. Its just for sake of demonstration.



vector<int>& f() {
    vector<int> a = *new vector<int>{15, 15, 16};
    return a;
}


int main () {
    
    vector<int>& b = f();
    
    for (auto x: b) {
        cout<<x<<endl;
    }
    

    
    cout<<"finished"<<endl;
}

嗨：

在上面的代码中，我使用动态分配的内存，以便向量 a 将其内存存储在堆上，这样就可以避免在函数退出后被删除。但由于某种原因，它没有。该代码给了我这个无法理解的错误：

=================================================================
==22==ERROR: AddressSanitizer: heap-use-after-free on address 0x602000000030 at pc 0x000000354a2c bp 0x7ffc1174eb30 sp 0x7ffc1174eb28
READ of size 4 at 0x602000000030 thread T0
    #1 0x7f2c73349082  (/lib/x86_64-linux-gnu/libc.so.6+0x24082)
0x602000000030 is located 0 bytes inside of 12-byte region [0x602000000030,0x60200000003c)
freed by thread T0 here:
    #3 0x7f2c73349082  (/lib/x86_64-linux-gnu/libc.so.6+0x24082)
previously allocated by thread T0 here:
    #5 0x7f2c73349082  (/lib/x86_64-linux-gnu/libc.so.6+0x24082)
Shadow bytes around the buggy address:
  0x0c047fff7fb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c047fff7fc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c047fff7fd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c047fff7fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c047fff7ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c047fff8000: fa fa 00 04 fa fa[fd]fd fa fa fa fa fa fa fa fa
  0x0c047fff8010: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8020: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8030: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8040: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8050: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07 
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
  Shadow gap:              cc
==22==ABORTING

我觉得我错过了一些东西——之后我会更恰当地重命名/改写我的问题。

Answer 1

vector<int>& f() {
    vector<int> a = *new vector<int>{15, 15, 16};
    return a;
}

这是调用

a

的复制构造函数并传递堆分配的对象，因为它具有值语义。

改用引用语义。

vector<int>& f() {
    vector<int>& a = *new vector<int>{15, 15, 16};
    return a;
}