Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people, just like you, are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
Solved

Allocation memory

Posted on 1998-06-11
5
239 Views
Last Modified: 2010-04-01
What does the (char *) do in this sample program?

#include<stdlib.h>

main()
{
char *str;
if ((str= (char *) malloc(100)) ==NULL)
 {
   printf("not enough memory to allocate buffer\n");
   exit(1);
 }
printf("String was allocated");
return 0;
}
0
Comment
Question by:program
  • 3
  • 2
5 Comments
 

Author Comment

by:program
ID: 1165701
Edited text of question
0
 
LVL 22

Accepted Solution

by:
nietod earned 100 total points
ID: 1165702
answer coming.
0
 
LVL 22

Expert Comment

by:nietod
ID: 1165703
The return value of malloc() is a pointer of type "void *".  This means it doesn't point to any defined type.  This is because malloc doesn't know what you want to use the memory for, so it returns this, sort of, generic pointer.    you must convert this pointer to something useful.  You do this using a type cast, which is to put a type name inside of parenthesis before the thing to be changed.  For example.

int i;
char *CPtr1  = &i; // error &i is an int* pointer, not a char * pointer.
char *CPtr2 =  (char *) &i; // Okay converted from int * to char *.

you can also use this with non-pointers, like

double D = 5;
char c = (char) D; // convert D to a char.

0
 

Author Comment

by:program
ID: 1165704
Thanks for the answer.  This question stumped many people at my
office who have C knowledge.
0
 
LVL 22

Expert Comment

by:nietod
ID: 1165705
One thing I should have said and didn't is that the new operator is type safe and malloc is not.   That is new creates memory of a particular type and returns a pointer to that type.  This is much better than malloc.  A C++ program should never need to use malloc()  (except in the case of implimenting operator new).
0

Featured Post

Free Tool: Path Explorer

An intuitive utility to help find the CSS path to UI elements on a webpage. These paths are used frequently in a variety of front-end development and QA automation tasks.

One of a set of tools we're offering as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Written by John Humphreys C++ Threading and the POSIX Library This article will cover the basic information that you need to know in order to make use of the POSIX threading library available for C and C++ on UNIX and most Linux systems.   [s…
Go is an acronym of golang, is a programming language developed Google in 2007. Go is a new language that is mostly in the C family, with significant input from Pascal/Modula/Oberon family. Hence Go arisen as low-level language with fast compilation…
The viewer will learn how to use the return statement in functions in C++. The video will also teach the user how to pass data to a function and have the function return data back for further processing.
The viewer will learn how to clear a vector as well as how to detect empty vectors in C++.

840 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question