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Mastering Algorithms with C
book

Mastering Algorithms with C

by Kyle Loudon
August 1999
Intermediate to advanced content levelIntermediate to advanced
560 pages
18h 57m
English
O'Reilly Media, Inc.
Content preview from Mastering Algorithms with C

Questions and Answers

Q: One of the difficulties with pointers is that often when we misuse them, our errors are not caught by the compiler at compile time; they occur at runtime. Which of the following result in compile-time errors? Which of the following result in runtime errors? Why?

a)

char *sptr = "abc",*tptr;
*tptr = sptr;

b)

char *sptr = "abc",*tptr;
tptr = sptr;

c)

char *sptr = "abc",*tptr;
*tptr = *sptr;

d)

int *iptr = (int *)10;
*iptr = 11;

e)

int *iptr = 10;
*iptr = 11;

f )

int *iptr = (int *)10;
iptr = NULL;

A: a) A compile-time error occurs because when we dereference tptr, we get a character, whereas sptr is a pointer to a character. Thus, the code is trying to assign a character pointer to a character, which is a type conflict. b) No error occurs because both tptr and sptr are character pointers. c) A runtime error is likely to occur because no storage has been allocated for tptr. When we dereference tptr, we cannot be sure where it points. d) A runtime error is likely to occur because assigning an integer pointer a fixed address is dangerous. When dereferencing iptr, we try to write 11 at address 10, which is probably invalid. e) A compile-time error or warning occurs because the code is trying to initialize an integer pointer to an integer, which is a type conflict. f ) No error occurs because although the code first performs the dangerous step of initializing iptr to a fixed address, it is then immediately reset to NULL, which is valid.

Q: Recall that calculations with ...

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Publisher Resources

ISBN: 1565924533Supplemental ContentErrata Page