GDB vector.size（）的值錯誤

Question

一個簡單的vector.push_back（）在我的代碼中導致一些錯誤：

#include <vector>
using namespace std;

int main(int argc, const char *argv[])
{
    vector<unsigned> stack;
    stack.push_back(1);
    stack.push_back(1); //stack.size() becomes 467369971 after this
    stack.push_back(1);
    stack.push_back(1);
    ... more push_back()s ...
    return 0;
}

我正在使用GDB來檢查其行為...而奇怪的是，第二個push_back（）之后stack.size（）出錯了。 變成467369971！ 有什么問題嗎？ 我使用的是Win7 64位，並且使用的是MinGW和G ++ 4.7.0

以下是GDB的輸出：

(gdb) n
5                       std::vector<unsigned> sta
(gdb) n
6                       stack.push_back(1);
(gdb) display stack.size()
1: stack.size() = 0
(gdb) n
7                       stack.push_back(1);
1: stack.size() = 1
(gdb)
8                       stack.push_back(1);
1: stack.size() = 467369971 //goes wrong here
(gdb)
9                       stack.push_back(1);
1: stack.size() = 467369971
(gdb)
10                      stack.push_back(1);
1: stack.size() = 4         // gets "normal"
(gdb)
11                      stack.push_back(1);
1: stack.size() = 467369971 // wrong again
(gdb)
12                      stack.push_back(1);
1: stack.size() = 6
(gdb)
13                      stack.push_back(1);
1: stack.size() = 7
(gdb)
14                      stack.push_back(1);
1: stack.size() = 8
(gdb)
15                      stack.push_back(1);
1: stack.size() = 467369971
(gdb)
16                      stack.push_back(1);
1: stack.size() = 10
(gdb)
17                      stack.push_back(1);
1: stack.size() = 11
(gdb)
18                      stack.push_back(1);
1: stack.size() = 12
(gdb)
19                      return 0;

Answer 1

有什么問題嗎？

這是您的編譯器或GDB中的錯誤。 在使用g++ (Ubuntu 4.4.3-4ubuntu5.1) 4.4.3和GDB 7.4的Linux上不會重現：

(gdb) n
7       stack.push_back(1);
1: stack.size() = 0
(gdb) 
8       stack.push_back(1); //stack.size() becomes 467369971 after this
1: stack.size() = 1
(gdb) 
9       stack.push_back(1);
1: stack.size() = 2
(gdb) 
10      stack.push_back(1);
1: stack.size() = 3
(gdb) 
11      stack.push_back(1);
1: stack.size() = 4
(gdb) 
12      stack.push_back(1); //stack.size() becomes 467369971 after this
1: stack.size() = 5
(gdb) 
13      stack.push_back(1);
1: stack.size() = 6
(gdb) 
14      stack.push_back(1);
1: stack.size() = 7
(gdb) 
15      return 0;
1: stack.size() = 8
(gdb) 
16  }
(gdb) q

不幸的是，要弄清楚應該歸咎於哪個工具將有些困難：您將需要檢查生成的debuginfo。 相反，您可以嘗試使用不同版本的GCC和GDB重現該問題。 如果變化的GCC導致該錯誤消失，則可能是GCC中的錯誤。 如果不同的GDB版本使該錯誤消失，則可能是GDB錯誤。