RE: [Dev-C++] dynamic allocation and structs

[Scott W. <se...@al...>]

Thanks for the replies to my question (and the entertaining discussion it
led to).  It was all very helpful.

Scott

-----Original Message-----
From: Per Westermark [mailto:pw...@ia...]
Sent: Thursday, October 24, 2002 9:13 AM
To: Scott Williams
Cc: dev...@li...
Subject: Re: [Dev-C++] dynamic allocation and structs



// Alternative 1, array of entries.
mystruct *myarray;
void func(int count) {
    int i;
    myarray = (mystruct*)malloc(count*sizeof(mystruct));
    for (i = 0; i < count; i++) {
        myarray[i].xx = yy;
    }
}

// Alternative 2, array of pointers to entries.
mystruct **myarray;
void func(int count) {
    int i;
    myarray = (mystruct**)malloc(count*sizeof(*mystruct));
    for (i = 0; i < count; i++) {
        myarray[i] = (mystruct*)malloc(sizeof(mystruct));
        myarray[i]->xx = yy;
    }
}

/Per W

On Thu, 24 Oct 2002, Scott Williams wrote:

> Hi,
>
> I'm working in C (no C++ please).  Got a couple of questions related to
> dynamic allocation and in particular, dynamically allocating an array of
> structs.
>
> First, what is the duration of memory allocated by malloc (etc.)?  In
> particular, I want to dynamically allocate/de-allocate several global
> variables within a single subroutine called from main and so want to be
sure
> that the allocated memory exists beyond the scope of that subroutine.
>
> Second, it is my understanding that it is perfectly acceptable to have an
> array of structs.  E.g.,
>
> struct mystruct {
>   double var1;
>   long   var2;
>   etc...
> }
>
> . . .
>
> struct mystruct data[100];
>
> Is this correct?  If so, what then is the calling sequence to dynamically
> allocate an array of structs, and, in particularly, make the result
> available globally?
>
> Thanks for your help (& sorry if this is naive).
>
> Scott Williams
>
>
>
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