Date: Sun, 2 Apr 1995 19:27:28 -0700 (PDT)
From: ".ASM SoftWare Systems" <rdc AT freenet DOT vancouver DOT bc DOT ca>
Subject: Re: Dynamic allocation question
To: Mat Hostetter <mat AT ardi DOT com>
Cc: djgpp AT sun DOT soe DOT clarkson DOT edu, IBBT0 AT cc DOT uab DOT es

On Sun, 2 Apr 1995, Mat Hostetter wrote:

> >>>>> "DJ" == DJ Delorie <dj AT delorie DOT com> writes:
> 
>     >> If ASSUMPTION 2 is true, is there an ANSI-C manner to get from
>     >> the O.S.  the amount of memory a pointer points to? I have
>     >> tried "sizeof(pointer)", but it only returns the size of a
>     >> single element.
> 
>     DJ> There is no portable way of doing this.  ANSI and POSIX
>     DJ> specifically stay away from memory allocation techniques.  In
>     DJ> theory, you may be able to reverse-engineer malloc() (or, for
> 
> Some people write their own my_malloc/my_realloc/my_free that keep
> track of the block size in a portable way and use these routines
> consistently.  What you do is allocate four bytes more than you need
> 


 The non-ANSI Standard way of doing these things is with functions like:

  unsigned __freect(sizeof(float))
          Returns # of items of size 'float' that can be allocated from free
          memory left in the heap.

  uint __memavl()
          Returns approx # of bytes of free mem left in the heap.

  unsigned __msize(char *ptr)
          Returns # of bytes allocated to ptr.

  uint stackavail()
          Returns # of bytes available for stack allocation using alloca().


  TurboC has functions like:

  int heapcheck(), heapfillfree(), heapcheckfree(), heapchecknode(), 
      heapwalk() and others ...


  If you understand how gcc's malloc works you can write a ONE version
specific function that does one of the above and incorporate it into your 
program. As long as you don't compile with a later (or earlier) version 
with an incompatable malloc method you'll be ok ...

 Veronica/WWW/Jughead for the above functions, you may find .c  !