Sponsored Content
Full Discussion: Help with malloc()
Top Forums UNIX for Dummies Questions & Answers Help with malloc() Post 302775729 by Don Cragun on Tuesday 5th of March 2013 10:28:06 AM
Old 03-05-2013
Quote:
Originally Posted by shamrock
Because the second argument of fgets is an integer while malloc returns pointer to void so take it out...
The problem is much deeper than that.

The given program allocates enough space to hold a pointer to a character; not enough space to read a line of user input. And, I don't see how eracav can preallocate space for "unlimited input from the user". In addition to that, eracav isn't checking the return value of malloc() to determine if space was allocated nor of fgets() to determine if an error or EOF has been encountered before a <newline> was found.

To do what needs to be done, eracav will need much more complicated logic with a loop calling fgets() and realloc() to increase the input buffer size until a <newline> or EOF has been copied into the growing buffer.

Is this a homework assignment?
This User Gave Thanks to Don Cragun For This Post:
 

10 More Discussions You Might Find Interesting

1. Programming

a problem about malloc()

1 . Thanks everyone who read the post. 2 . the programe is that : #include <stdio.h> #include <string.h> void do_it(char *p) { p = (char *) malloc(100); (void )strcpy(p,"1234"); } int main(void) { char *p; do_it(p); (void )printf("p = %s \n",p); (1 Reply)
Discussion started by: chenhao_no1
1 Replies

2. Programming

malloc

hello sir since by mentioning a integer pointer and storing the integers by incrementing the pointer value then what is the purpose of malloc? u can decalre it as in t *p; several integers can be stored by incrementing the value of p, hence what is the diffrence between this... (2 Replies)
Discussion started by: rajashekaran
2 Replies

3. Programming

When to use Malloc?

Hi! I hope this is the correct forum to post the question even if I'm a newbie... I am a C-newbie (and really on the edge to be a C-addict ;) ) and have a question. When should I use malloc? To state it differently, when should I NOT use malloc? For instance, if I have an array of... (5 Replies)
Discussion started by: Tonje
5 Replies

4. Programming

malloc()

Some one please explain me what is Dynamic memory allocation and the use of malloc() function.How do we allocate memory dynamically and also the other way? (3 Replies)
Discussion started by: rash123
3 Replies

5. Programming

Malloc implementation in C

Hey Guys I am trying to implement the malloc function for my OS class and I am having a little trouble with it. I would be really grateful if I could get some hints on this problem. So I am using a doubly-linked list as my data structure and I have to allocate memory for it (duh...). The... (1 Reply)
Discussion started by: Gambit_b
1 Replies

6. UNIX for Advanced & Expert Users

Malloc Implementation in C

Hey Guys Some of my friends have got together and we are trying to write a basic kernel similar to Linux. I am trying to implement the malloc function in C and I am using a doubly linked list as the primary data structure. I need to allocate memory for this link list (duh...) and I don't feel... (2 Replies)
Discussion started by: rbansal2
2 Replies

7. Programming

malloc vs realloc

Why when using realloc, john is reversed 3 times but not the other 2 names ? But if I use malloc, then the 3 names are reversed correctly ? (but then there is a memory leak) How can I reverse all 3 names without a memory leak ? char *BUFFER = NULL; char *STRREVERSE(const char *STRING) {... (5 Replies)
Discussion started by: cyler
5 Replies

8. UNIX for Dummies Questions & Answers

Kmalloc and malloc

Do kmalloc and malloc allocate from same heap ? (3 Replies)
Discussion started by: dragonpoint
3 Replies

9. Programming

help with malloc [solved]

Hi i found code in google how to malloc an 2D array and i tried that : #include<stdio.h> #include<stdlib.h> int **A; int **B; int main(int argc,char *argv) { printf("name of text : %s\n",argv); //read arrays int i,j; int l,m; int M,n; FILE *fp; fp=fopen(argv,"r"); ... (0 Replies)
Discussion started by: giampoul
0 Replies

10. Programming

malloc vs new speed

Which one is faster among malloc and new? My understanding is that since new also has to call constructors after allocating memory it must be slower than malloc. Am I correct? (1 Reply)
Discussion started by: rupeshkp728
1 Replies
MALLOC_ZONE_MALLOC(3)					   BSD Library Functions Manual 				     MALLOC_ZONE_MALLOC(3)

NAME
malloc_create_zone, malloc_destroy_zone, malloc_default_zone, malloc_zone_from_ptr, malloc_zone_malloc, malloc_zone_calloc, malloc_zone_valloc, malloc_zone_realloc, malloc_zone_memalign, malloc_zone_free -- zone-based memory allocation SYNOPSIS
#include <malloc/malloc.h> malloc_zone_t * malloc_create_zone(vm_size_t start_size, unsigned flags); void malloc_destroy_zone(malloc_zone_t *zone); malloc_zone_t * malloc_default_zone(void); malloc_zone_t * malloc_zone_from_ptr(const void *ptr); void * malloc_zone_malloc(malloc_zone_t *zone, size_t size); void * malloc_zone_calloc(malloc_zone_t *zone, size_t num_items, size_t size); void * malloc_zone_valloc(malloc_zone_t *zone, size_t size); void * malloc_zone_realloc(malloc_zone_t *zone, void *ptr, size_t size); void * malloc_zone_memalign(malloc_zone_t *zone, size_t alignment, size_t size); void malloc_zone_free(malloc_zone_t *zone, void *ptr); DESCRIPTION
The malloc_create_zone() function creates a malloc zone, advising an initial allocation of start_size bytes, and specifying flags that alter the standard behavior of the zone. The returned malloc zone can be used to provide custom allocation and deallocation behavior, and to retrieve additional information about the allocations in that zone. The malloc_destroy_zone() function deallocates all memory associated with objects in zone as well as zone itself. The malloc_default_zone() function returns the default system malloc zone, used by malloc(3), and free(3). The malloc_zone_from_ptr() function returns a pointer to the malloc zone which contains ptr or NULL, if the pointer does not point to an allocated object in any current malloc zone. The malloc_zone_malloc(), malloc_zone_calloc(), malloc_zone_valloc(), malloc_zone_realloc(), malloc_zone_memalign(), and malloc_zone_free() perform the same task on zone as their non-prefixed variants, malloc(3), calloc(3), valloc(3), realloc(3), posix_memalign(3), and free(3) perform on the default system malloc zone. RETURN VALUES
The malloc_create_zone(), malloc_default_zone(), and malloc_zone_from_ptr() functions return a pointer to a malloc_zone_t structure, or NULL if there was an error. The malloc_zone_malloc(), malloc_zone_calloc(), malloc_zone_valloc(), malloc_zone_realloc(), and malloc_zone_memalign() functions return a pointer to allocated memory. If there is an error, they return a NULL pointer. They are not required to set errno. SEE ALSO
malloc(3), posix_memalign(3) BSD
Aug 13, 2008 BSD
All times are GMT -4. The time now is 04:28 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy