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0x0C. C - More malloc, free

Resources

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Learning Objectives

General

  • How to use the exit function
  • What are the functions calloc and realloc from the standard library and how to use them

Tasks

0. Trust no one

  • Write a function that allocates memory using malloc.

Requirements:

Prototype: void *malloc_checked(unsigned int b); Returns a pointer to the allocated memory if malloc fails, the malloc_checked function should cause normal process termination with a status value of 98

Mode: mandatory

File: 0-malloc_checked.c

1. string_nconcat

  • Write a function that concatenates two strings.

Requirements:

Prototype: char *string_nconcat(char *s1, char *s2, unsigned int n); The returned pointer shall point to a newly allocated space in memory, which contains s1, followed by the first n bytes of s2, and null terminated If the function fails, it should return NULL If n is greater or equal to the length of s2 then use the entire string s2 if NULL is passed, treat it as an empty string

Mode: mandatory

File: 1-string_nconcat.c

2. _calloc

  • Write a function that allocates memory for an array, using malloc.

Requirements:

Prototype: void *_calloc(unsigned int nmemb, unsigned int size); The _calloc function allocates memory for an array of nmemb elements of size bytes each and returns a pointer to the allocated memory. The memory is set to zero If nmemb or size is 0, then _calloc returns NULL If malloc fails, then _calloc returns NULL

Mode: mandatory

File: 2-calloc.c

3. array_range

  • Write a function that creates an array of integers.

Requirements:

Prototype: int *array_range(int min, int max); The array created should contain all the values from min (included) to max (included), ordered from min to max Return: the pointer to the newly created array If min > max, return NULL If malloc fails, return NULL

Mode: mandatory

File: 3-array_range.c

4. _realloc

  • Write a function that reallocates a memory block using malloc and free

Requirements:

Prototype: void *_realloc(void *ptr, unsigned int old_size, unsigned int new_size); where ptr is a pointer to the memory previously allocated with a call to malloc: malloc(old_size) old_size is the size, in bytes, of the allocated space for ptr and new_size is the new size, in bytes of the new memory block The contents will be copied to the newly allocated space, in the range from the start of ptr up to the minimum of the old and new sizes If new_size > old_size, the “added” memory should not be initialized If new_size == old_size do not do anything and return ptr If ptr is NULL, then the call is equivalent to malloc(new_size), for all values of old_size and new_size If new_size is equal to zero, and ptr is not NULL, then the call is equivalent to free(ptr). Return NULL Don’t forget to free ptr when it makes sense

Mode: #advanced

File: 100-realloc.c

5. We must accept finite disappointment, but never lose infinite hope

  • Write a program that multiplies two positive numbers.

Requirements:

Usage: mul num1 num2 num1 and num2 will be passed in base 10 Print the result, followed by a new line If the number of arguments is incorrect, print Error, followed by a new line, and exit with a status of 98 num1 and num2 should only be composed of digits. If not, print Error, followed by a new line, and exit with a status of 98 You are allowed to use more than 5 functions in your file

Mode: #advanced

File: 101-mul.c