Question

My program seems to always produce ridiculous errors.
Please provide directions for me. The following code segment cutout all irrelevant parts.
Thanks.

Part A of the code segment seems failed to initialize the array correctly, how to debug?
Part B of the code segment always crash, is there anything i missed?

---

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!
}

---

Sample Output

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

---

• Platform: win 7 x64
• Compiler: 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";
   }

And here

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

you’re going out of bounds. The last valid index is AG_TOTAL.

You’ve got undefined behaviour (UB). The errors are only as ridiculous as UB can be.