I'm learning C/C as a newcomer from java in school and since it is weekend, I can't get help from there. I got an error like this:

==18== 0 bytes in 1 blocks are definitely lost in loss record 1 of 1
==18==    at 0x483C583: operator new[](unsigned long) (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
==18==    by 0x109536: Table::Table(unsigned long) (taul2.cpp:38)
==18==    by 0x1093CF: main (taul2.cpp:108)

main:

  Table nums(7);
  nums.add(1); nums.add(2);
  cout << nums<< endl;
  Table nums2;
  taul.place(nums);
  cout << nums2<< endl;

  Table nums3;  // line 108
  cout << nums3 << endl;

  return 0;

Table:

class Table{
    size_t max_size;
    size_t amount;
    int *numbers;
    int fail;
public:
Table(size_t size=0) 
{
    fail= 0;
    max_size = 0;
    numbers = new int[size]; // line 38
    if ( numbers ) max_size = size;
    lkm = 0;
}
  ~Table() { if ( max_size != 0 ) delete [] numbers; max_size = 0; }
/* ... */
}

The error only occurs on nums3 which length is 0, debugger shows that it goes to the ~Table method, just like all the others, but it is the only 1 with errors.

CodePudding user response：

Even if you new 0 bytes, you still have to delete it. With every allocation, there's a bit of additional overhead beyond the number of bytes you asked for. (e.g. entry in the heap, the pointer itself, etc...).

Side note: new items[0] does not return nullptr. And even if it did, delete [] nullptr is perfectly OK and safe.

Change your destructor from

~Table() { if ( max_size != 0 ) delete [] numbers; max_size = 0; }

To this:

~Table() { 
    delete [] numbers;
}