Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!tut.cis.ohio-state.edu!ucbvax!ulysses!ulysses.att.com!mwb
From: mwb@ulysses.att.com (Michael W. Balk)
Newsgroups: comp.lang.c
Subject: Re: Memory allocation / data access
Summary: malloc error
Message-ID: <14477@ulysses.att.com>
Date: 16 Mar 91 23:26:29 GMT
References: <29491@cs.yale.edu>
Sender: netnews@ulysses.att.com
Distribution: na
Lines: 35

In article <29491@cs.yale.edu>, jim@doctor.chem.yale.edu (James F. Blake) writes:
> 
> I have two questions: 1) Have I allocated the storage properly and 2) Is this
> the most efficient way to access the data (i.e., monomer[].atom[].x).  
> I am allocating storage for n-molecules, each with n-atoms and 3 coordinates.
> Any information would be greatly appreciated.
> 
> 
	.
	.
	.
> 
> if ((monomer = (solvent *) malloc (nmol * sizeof (solvent *)))==NULL)
>   exit(1);

	.
	.
	.


In answer to your first question I see an error in malloc.
Instead of sizeof(solvent *), you should have sizeof(solvent), i.e.,
you want to allocate space for nmol of solvent, not pointers to solvent.
Malloc then returns a pointer to the start of this space (type char* or void*),
which you have then correctly cast to a pointer to solvent.






Michael W. Balk
AT&T Bell Laboratories
Murray Hill, NJ 07974
mwb@ulysses.att.com