Memory mixed review

Questions 1 to 5 of 6

1. 1. What does this program print? ``cpp #include <cstddef> #include <iostream> struct Mix { char a; short b; char c; }; int main() { std::cout << sizeof(Mix) << ' ' << offsetof(Mix, c) << '\n'; return 0; } ``

   4 46 48 46 2
2. 2. What does this program print? ``cpp #include <iostream> struct Node { int value; Node* next; }; int main() { Node c{3, nullptr}; Node b{2, &c}; Node a{1, &b}; Node* head = &a; head = head->next; head->next = head->next->next; for (Node* cur = head; cur != nullptr; cur = cur->next) { std::cout << cur->value << '\n'; } std::cout << "a.next->value = " << a.next->value << '\n'; return 0; } ``

   Two lines: 2, then a.next->value = 2Three lines: 1, 2, 3, then a.next->value = 1Two lines: 2, then a.next->value = 3Two lines: 1, then a.next->value = 1
3. 3. Match each term from the shared ownership and leaks lessons to its meaning.

   Choose the matching item for each row.

   weak_ptrChoose…no pointer in the program can reach the block any morea global or static variable still reaches the block, so a leak checker stays silentneither count reaches 0, so neither object is ever freedlooks at an object without owning it; lock() returns an empty pointer once the object is gonetwo shared_ptr objects that own each otherChoose…no pointer in the program can reach the block any morea global or static variable still reaches the block, so a leak checker stays silentneither count reaches 0, so neither object is ever freedlooks at an object without owning it; lock() returns an empty pointer once the object is gonelost memoryChoose…no pointer in the program can reach the block any morea global or static variable still reaches the block, so a leak checker stays silentneither count reaches 0, so neither object is ever freedlooks at an object without owning it; lock() returns an empty pointer once the object is gonekept memoryChoose…no pointer in the program can reach the block any morea global or static variable still reaches the block, so a leak checker stays silentneither count reaches 0, so neither object is ever freedlooks at an object without owning it; lock() returns an empty pointer once the object is gone
4. 4. Match each value from the row-major, cache, stack and const lessons to what it is.

   Choose the matching item for each row.

   position of grid[r][c] in a row-major array with C columnsChoose…64 bytes, which holds 16 ints139, which is 128 plus signal 11 (SIGSEGV)the address is fixed, but the value it points at can changer * C + ccache line on the test machineChoose…64 bytes, which holds 16 ints139, which is 128 plus signal 11 (SIGSEGV)the address is fixed, but the value it points at can changer * C + cexit code of a C++ program that overflows the stackChoose…64 bytes, which holds 16 ints139, which is 128 plus signal 11 (SIGSEGV)the address is fixed, but the value it points at can changer * C + cint* const qChoose…64 bytes, which holds 16 ints139, which is 128 plus signal 11 (SIGSEGV)the address is fixed, but the value it points at can changer * C + c
5. 5. A dangling pointer still holds an address that is not zero. Why can a p != nullptr check not catch a read through it?

   delete sets the pointer to nullptr only in debug buildsThe compiler removes the check when it sees a delete before itThe check only asks whether the address is zero, and a freed address is not zeroThe check reads the freed memory, which hides the bug from the sanitizer