指针和指针指向的指针

Question

Update : Sorry, just a big mistake. It is meaningless to write int *a = 3; But please just think the analogy to the case like TCHAR *a = TEXT("text") ; (I edited my question, so some answers and comments are strange, since they are for my original question which is not suitable)

In main function, suppose I have a pointer TCHAR *a = TEXT("text"); Then it excutes the following code:

int i;
for (i = 0; i < 1000; i++) {
        a = test(i);
}

with the function TCHAR* test(int par) defined by:

TCHAR* test(int par)
{
    TCHAR *b = TEXT("aaa");
    return b;
}

My question is, after executing the above code, but before the program ends, in the memory:

    1. the pointer `a` remains?
    2. The 1000 pointers `b` are deleted each time the function test(...) exits ?
    3. But there are still 1000 memory blocks there?

---

In fact, my question is motivated from the following code, which shows a tooltip when mouse is over a tab item in a tab control with the style TCS_TOOLTIPS:

case WM_NOTIFY
    if (lpnmhdr->code == TTN_GETDISPINFO) {
    LPNMTTDISPINFO lpnmtdi;
    lpnmtdi = (LPNMTTDISPINFO)lParam;

    int tabIndex = (int) wParam; // wParam is the index of the tab item.

            lpnmtdi->lpszText = SetTabToolTipText(panel->gWin.At(tabIndex));
            break;
    }

I am thinking if the memory usage increases each time it calls

SetTabToolTipText(panel->gWin.At(tabIndex)) , which manipulates with TCHAR and TCHAR* and return a value of type LPTSTR .

Answer 1

You dont allocate any memory so you don't have to worry about memory being freed. When your vaiables go out of scope they will be freed automatically. In this function

 int test(int par)
 {
    int *b = par;
 }

you don't have a return value even though the function says that is will return an int , so you should probably do so as in this line

for (i = 0; i < 1000; i++) {
    a = test(i);
}

you assign to a the value that is returned by test() . Also

int* a = 3;
int* b = par;

are asking for trouble. You are assigning integer values to a pointer variable. You should probably rethink your above code.

Answer 2

1. Yes, the pointer a remains till we return from the main function
2. The variable b (a 4-byte pointer) is automatic. It is created each time we call test function. Once we return from it, the variable disappears (the pointer). Please note, the value to which b points isn't affected.
3. No. In most of the cases, I think, there will be only one block allocated during compilation time (most likely in the read-only memory) and the function will be returning the same pointer on every invocation.

If SetTabToolTipText allocates a string inside using some memory management facilities new/malloc or some os-specific, you should do an additional cleanup. Otherwise there'll be a memory leak.

If nothing like this happens inside (it's not mentioned in the documentation or comments etc), it's most likely returning the pointer to some internal buffer which you typically use as readonly. In this case, there should be no concerns about a memory consumption increase.

Answer 3

指针应该包含地址...所以int* a = 3是没有意义的......并且在函数中你没有为int分配内存（仅用于par变量，然后在函数结束时销毁），你分配内存用于存储在int* b ，当函数结束时，这个内存也是空闲的。