Andrew login ID:Full Name:Section:15-213/18-243, Fall 2010Exam 2Tuesday, November 9. 2010Instructions:• Make sure that your exam is not missing any sheets, then write your Andrew login ID, full name, andsection on the front.• This exam is closed book, closed notes, although you may use a single 8 1/2 x 11 sheet of paper withyour own notes. You may not use any electronic devices.• Write your answers in the space provided below the problem. If you make a mess, clearly indicateyour final answer.• The exam has a maximum score of 67 points.• The problems are of varying difficulty. The point value of each problem is indicated. Good luck!1 (10):2 (06):3 (12):4 (09):5 (09):6 (12):7 (09):TOTAL (67):Page 1 of 15Problem 1. (10 points):Multiple choice on a variety of topics. Write the correct answer for each question in the following table:1 2 3 4 5 6 7 8 9 101. For the Unix linker, which of the following accurately describes the difference between global sym-bols and local symbols?(a) There is no functional difference as to how they can be used or how they are declared.(b) Global symbols can be referenced by other modules (files), but local symbols can only be refer-enced by the module that defines them.(c) Global symbols refer to variables that are stored in .data or .bss, while local symbols referto variables that are stored on the stack.(d) Both global and local symbols can be accessed from external modules, but local symbols aredeclared with the “static” keyword.2. Consider the following C variable declarationint*(*f[3])();Then f is(a) an array of pointers to pointers to functions that return int(b) a pointer to an array of functions that return pointers to int(c) a function that returns a pointer to an array of pointers to int(d) an array of pointers to functions that return pointers to int(e) a pointer to a function that returns an array of pointers to int(f) a pointer to an array of pointers to functions that return intHint: Recall from the K&R book that [] and () have higher precedence than*.3. Which of the following is true concerning dynamic memory allocation?(a) External fragmentation is caused by chunks which are marked as allocated but actually cannotbeing used.(b) Internal fragmentation is caused by padding for alignment purposes and by overhead to maintainthe heap data structure (such as headers and footers).(c) Coalescing while traversing the list during calls to malloc is known as immediate coalescing.(d) Garbage collection, employed by calloc, refers to the practice of zeroing memory before use.Page 2 of 15For the next 3 questions, consider the following code running on a 32-bit Linux system. Recall thatcalloc zeros the memory that it allocates.int main(){long a,*b, c;char**p;p = calloc(8, sizeof(char)); /*calloc returns 0x1dce1000*/a = (long) (p + 0x100);b = (long*) (*p + 0x200);c = (int) (b + 0x300);printf("p=%p a=%x b=%p c=%x\n", p, a, b, c);exit(0);}4. When printf is called, what is the hex value of variable a?(a) Can’t tell(b) 0x1dce1100(c) 0x1dce1400(d) 0x1dce18005. When printf is called, what is the hex value of variable b?(a) Can’t tell(b) 0x1dce1200(c) 0x1dce2000(d) 0x200(e) 0x8006. When printf is called, what is the hex value of variable c?(a) Can’t tell(b) 0x1dce2a00(c) 0x1dce4400(d) 0xc00(e) 0xe00Page 3 of 157. Which of the following is not a default action for any signal type?(a) The process terminates.(b) The process reaps the zombies in the waitlist.(c) The process stops until restarted by a SIGCONT signal.(d) The process ignores the signal.(e) The process terminates and dumps core.8. A system uses a two-way set-associative cache with 16 sets and 64-byte blocks. Which set does thebyte with the address 0xdeadbeef map to?(a) Set 7(b) Set 11(c) Set 13(d) Set 149. When it succeeds, execve is called once and returns how many times?(a) 0(b) 1(c) 2(d) 310. When it suceeds, fork is called once and returns how many times?(a) 0(b) 1(c) 2(d) 3Page 4 of 15Problem 2. (6 points):Linking. Consider the executable object file a.out, which is compiled and linked using the commandunix> gcc -o a.out main.c foo.cand where the files main.c and foo.c consist of the following code:/*main.c*/#include <stdio.h>static int a = 1;int b = 2;int c;int main(){int c = 3;foo();printf("a=%d, b=%d, c=%d\n", a, b, c);return 0;}/*foo.c*/int a, b, c;void foo(){a = 4;b = 5;c = 6;}What is the output of a.out?Answer: a=____, b=_____, c=_____Page 5 of 15Problem 3. (12 points):Cache Operation In this problem, you are asked to simulate the operation of a cache. You can make thefollowing assumptions:• There is only one level of cache• Physical addresses are 8 bits long (m = 8)• The block size is 4 bytes (B = 4)• The cache has 4 sets (S = 4)• The cache is direct mapped (E = 1)(a) What is the total capacity of the cache? (in number of data bytes)(b) How long is a tag? (in number of bits)(c) Assuming that the cache starts clean (all lines invalid), please fill in the following tables, describingwhat happens with each operation. Addresses are given in both hex and binary for your convenience.Operation Set index? Hit or Miss? Eviction?load 0x00 (0000 0000)20 miss noload 0x04 (0000 0100)2missload 0x08 (0000 1000)2store 0x12 (0001 0010)20load 0x16 (0001 0110)2store 0x06 (0000 0110)2load 0x18 (0001 1000)22load 0x20 (0010 0000)2store 0x1A (0001 1010)2Page 6 of 15Problem 4. (9 points):Signals. Consider the following three different snippets of C code. Assume that all functions and proceduresreturn correctly and that all variables are declared and initialized properly. Also, assume that an arbitrarynumber of SIGINT signals, and only SIGINT signals, can be sent to the code snippets randomly from someexternal source.For each code snippet, circle the value(s) of i that could possibly be printed by the printf command atthe end of each program. Careful: There may be more than one correct answer for each question. Circle allthe answers that could be correct.Code Snippet 1:int i = 0;void handler(int sig) {i = 0;}int main() {int j;signal(SIGINT, handler);for (j=0; j < 100; j++) {i++;sleep(1);}printf("i = %d\n", i);exit(0);}Code Snippet 2:int i = 0;void handler(int sig) {i = 0;}int main () {int j;sigset_t s;signal(SIGINT, handler);/*Assume that s has beeninitialized and declaredproperly for SIGINT*/sigprocmask(SIG_BLOCK, &s, 0);for (j=0; j < 100; j++) {i++;sleep(1);}sigprocmask(SIG_UNBLOCK, &s, 0);printf("i = %d\n", i);exit(0);}Code Snippet 3:int i = 0;void handler(int sig) {i =
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