From: Jih-Shin Ho <u7711501 AT bicmos DOT ee DOT nctu DOT edu DOT tw>
Subject: Re: Malloc
To: john AT umdsun2 DOT umd DOT umich DOT edu (john hoeschele)
Date: Sat, 10 Dec 94 18:44:42 WST
Cc: djgpp AT sun DOT soe DOT clarkson DOT edu (djgpp)

> 
> I am trying to use malloc to allocate a 2.7Mbyte chunk of memory.  The 
> program compiles with no problems but when I try to execute, no memory is 
> allocated and it quits.  Here is how the function is used:
> 
> typedef struct sBuf {
>                UCHAR vmbuf[1728];
> }tBuf
> 
> tBuf *Bptr[1600];
> 
> inside main:
> 
> if(Bptr[0] = (tBuf *)malloc(1728*sizeof(tBuf)))
>    printf("There has been an error is allocating memory!!");
>    exit(1);

 It should be 'if (!(Bptr[0] = (tBuf *)malloc(1728*sizeof(tBuf))))'
 You forget '!'.

> 
> if it continues, I load Bptr[] with 1600 pointers to various locations in 
> allocated memory, but I never get there.  I always get the printf statement.
> 
> Am I using the malloc function wrong?  I tried a test program not using a 
> structure but just putting in large numbers to equal out to 2.7Meg, and 
> it returned an address ,so there is enough memory available.
> 
> I thought about just using a two dimensional array (array[1728][1600])

Your array is [1728][1728].
I suggest that you use another definition:
  UCHAR (*Bptr)[1600];

  Bptr = (UCHAR (*)[1600])malloc(1728 * 1600 * sizeof(UCHAR));

You will get 2D array ([1728][1600]).


  -- Jih-Shin Ho