After class exercises

Here are some exercises for toning your C muscles. NOTE: In the below text:

 #define IF_WRONG_CORRECT_IT "Is there something wrong with this code? How would you correct it?"

Dynamic Memory Management

• EASY: Write the memory diagram for the program in mallocDemo1.c. Specifically, (1) show where wordArray is stored; (2) where is word pointing to before and after malloc; (2) what is stored in the word? (3) What happens to wordArray after free? Compare this memory allocation with mallocDemo1.c

• EASY: In mallocDemo1.c, what happens if we add the below code after malloc ?

  word = wordArray;

  What do you expect when free function is called?

• EASY: In mallocDemo1.c, what happens if we add the below code instead of the exsting strcpy ?

  strcpy(word, wordArray[3]);

  Assume that the user has entered a wordArray of length 15 (say "pointers are fun")

• EASY: In mallocDemo1.c, what happens if we dont free word?

• EASY: When does malloc return NULL? Write a sample program to simulate 3 cases where malloc returns NULL. (man malloc)

• EASY: Dead objects and dangling pointers: What happens if we use word after the free call? Remember we have free'd the memory, but we are trying to access it. What should happen?

• EASY: Memory leaks: Say, I have a function

  void runMe(){
     int* leakingPtr = (int*) malloc(sizeof(int)*1024);
     for(int i=0;i<1024;i++){
       leakingPtr[i] = i+1000;
     }
   }
  

  Assume that I call runMe in the main. How does the heap look before and after the runMe call? What is wrong in the function?