c – vector.size()的GDB错误值

一个简单的vector.push_back()会在我的代码中导致一些错误：

#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来检查它的行为……而奇怪的是,在第二个push_back()之后,stack.size()出错了.变成467369971！可能有什么不对？我在Win7 64位上运行,而我正在使用MinGW和G 4.7.0

以下是GDB的输出：

(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;

解决方法

What may be wrong?

这是编译器或GDB中的错误.它不能在Linux上使用g(Ubuntu 4.4.3-4ubuntu5.1)4.4.3和GDB 7.4重现：

(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,弄清楚哪个工具应该归咎于这将有点困难：你需要检查生成的debuginfo.相反,您可能会尝试使用不同版本的GCC和GDB重现问题.如果变化的GCC导致bug消失,那么它可能是GCC中的一个错误.如果不同的GDB版本使bug消失,那可能是GDB错误.