barry> I'm a little confused about pointers in a specific case. ...[snip]
barry> My question is, why do output lines 3: and 5: give the same
pointer value?
[snip]
barry> My assumption was that line 5: would get the address of the
pointer that's a
barry> member of mys2, but it gets the address of the struct mys2 instead.
barry> Is this expected behaviour? And if so why?
It is expected, and this is why.
> printf("3: s2: %p\n", mys2);
This prints the starting address of struct 2 - that is obvious.
> printf("5: s1m: %p\n", &mys2 -> mptr);
To answer your question, why is this 3 & 5 the same - ask this question:
What is the byte offset of the 1st member of a structure?
The answer is ZERO of course, and what is the value of "PTR + ZERO"?
The next question is: What is the byte offset of the 2nd element of a
structure?
The answer is
(1) the size of the first element.
(2) PLUS any required alignment of the current element.
Consider:
struct {
char c;
uint32_t x;
};
In the above - try various types for the member X.
The last question is: What is the size of the total structure?
The answer is: The above - rounded to the alignment of the most
restrictive member of the structure.
-Duane.
