c++ - CPP : Mysterious error for array initialization and crash?

Question

我的程序似乎总是会产生荒谬的错误。请给我指路。下面的代码段删掉了所有不相关的部分。谢谢。

代码段A部分似乎没有正确初始化数组，如何调试？代码段的 B 部分总是崩溃，我是否遗漏了什么？

---

typedef unsigned long T_PSIZE;
int main()
{
   int AG_TOTAL = 6 ;
   /* part A1 */
   T_PSIZE* cntPeopleByAge = new T_PSIZE[AG_TOTAL + 1];
   /* part A2 - originally i use static array like this, but it also fails */
   //T_PSIZE cntPeopleByAge T_PSIZE[AG_TOTAL + 1];
   for (int i = 0; i < (AG_TOTAL + 1); i++)
   {
     std::cout << i << ":" << cntPeopleByAge[i] << "\t";
     cntPeopleByAge[i] = 0;
     std::cout << cntPeopleByAge[i] << "\n";
   }
   std::cout << "cntPeopleByAge:" << cntPeopleByAge[ AG_TOTAL + 1 ] << "\n";
   /* part B */
   delete [] cntPeopleByAge;
   return 0; // <---  crash here!
}

---

示例输出

0:200320        0
1:201581        0
2:201582        0
3:201583        0
4:0     0
5:0     0
cntPeopleByAge:1799119387:0:0

---

• 平台:win 7 x64
• 编译器:TDM-GCC x64

Answer 1

for (int i = 0; i < (AG_TOTAL + 1); i++)
   {
     std::cout << i << ":" << cntPeopleByAge[i] << "\t";
     //                       ^^^^^^^^^^^^^^^^
     // You're reading uninitialized memory here

     cntPeopleByAge[i] = 0;
     std::cout << cntPeopleByAge[i] << "\n";
   }

这里

std::cout << "cntPeopleByAge:" << cntPeopleByAge[ AG_TOTAL + 1 ] << "\n";

你越界了。最后一个有效索引是 AG_TOTAL。

您有未定义的行为 (UB)。这些错误只是和 UB 一样荒谬。