Compiler Design MCQs - Runtime Environments and Symbol Tables (Set 5)

Q1. Which of the following is NOT normally stored in a procedure's activation record?

a) The control link

b) Saved machine status such as the return address

c) The compiler's symbol table for the source program

d) Local variables of the procedure

Q2. The control link (dynamic link) in an activation record points to

a) the activation record of the lexically enclosing procedure

b) the start of the heap

c) the code of the called procedure

d) the activation record of the caller

Q3. In a language with nested procedures and static scoping, the access link is used to

a) return control to the caller

b) locate non-local variables declared in lexically enclosing procedures

c) allocate space on the heap

d) pass parameters by reference

Q4. Which language feature cannot be supported if all storage is allocated statically at compile time?

a) Global variables

b) Fixed-size arrays

c) Constant literals

d) Recursive procedure calls

Q5. Heap allocation, rather than stack allocation, is required when

a) a procedure has only integer locals

b) a procedure is called exactly once

c) a variable is declared constant

d) data must outlive the activation of the procedure that created it

Q6. Assume both parameters are passed by reference. What value of a is printed?

void f(int x, int y) {
    x = x + 1;
    y = y + x;
}

main:
    a = 2;
    f(a, a);
    print(a);

a) 2

b) 6

c) 3

d) 5

Q7. Call by name is typically implemented by passing

a) a thunk, a small routine that evaluates the argument expression in the caller's environment each time it is used

b) the address of the argument evaluated once at the call

c) a copy of the argument's value

d) the symbol table entry of the argument

Q8. Using call by value-result, what two values are printed, in order?

int g = 10;
void p(int x) {
    x = 20;
    print(g);
}

main:
    p(g);
    print(g);

a) 10 then 10

b) 20 then 20

c) 10 then 20

d) 20 then 10

Q9. A dangling reference most commonly arises when

a) a function returns a pointer to one of its own local variables

b) a global variable is never used

c) a heap object is still reachable

d) a parameter is passed by value

Q10. What is printed when the program below runs under dynamic scoping?

int x = 1;
void show() { print(x); }
void test() { int x = 5; show(); }

main:
    test();
    show();

a) 1 1

b) 5 5

c) 1 5

d) 5 1

Q11. With a display used for non-local access, reaching a variable declared k nesting levels out requires

a) exactly k access-link traversals

b) a constant number of memory accesses, independent of k

c) a search of the symbol table at runtime

d) k squared memory accesses

Q12. Which data structure gives the fastest average-case lookup for identifiers in a compiler's symbol table?

a) Unsorted linear list

b) Hash table

c) Singly linked list sorted by insertion time

d) Binary search tree built from sorted input

Q13. Which symbol table organisation most naturally supports nested block scopes?

a) A single list with no scope information

b) One global hash table that never removes entries

c) A stack or chain of tables, one per scope, searched from the innermost outward

d) A sorted array of all identifiers in the program

Q14. A procedure at nesting depth 3 calls a procedure declared at nesting depth 2. How many access links must be followed from the caller to set the callee's access link?

a) 0

b) 2

c) 1

d) 3

Q15. In a typical runtime memory layout, how are the stack and heap arranged?

a) They grow towards each other through a shared free area

b) Both grow in the same direction from the code area

c) The heap is placed inside the stack

d) Their sizes are fixed at compile time

Q16. Which garbage collection technique, used on its own, fails to reclaim cyclic data structures that are no longer reachable?

a) Reference counting

b) Mark and sweep

c) Copying collection

d) Generational tracing collection

Q17. How many activations of fib occur, that is, how many fib nodes are in the activation tree, for the call fib(3)?

int fib(int n) {
    if (n < 2) return n;
    return fib(n - 1) + fib(n - 2);
}

a) 5

b) 3

c) 4

d) 8

Q18. Which piece of information is NOT normally kept in a compiler's symbol table entry for a variable?

a) Its name

b) Its data type

c) The variable's value at each step of program execution

d) Its scope or nesting level