Malloc a struct
 

Hello guys..
I´m trying to do something like the code below ..

struct node{

       int a;

       char *s;

};        



void main()

{

    node *x;

    int sMAX = 3;

    int nodeMAX = 10;

      

    x = (node*)malloc((sizeof(int)+sizeof(char)*sMAX)*nodeMAX);

...

}

in other words I want to alloc dynamically the number of nodes and also the length of s in node struct
I tried a lot of things like:

x = (node*)malloc((sizeof(node)*nodeMAX);

x = (node*)malloc((sizeof(struct node)*nodeMAX);

x = (node*)malloc((sizeof(node)+sizeof(char)*sMAX)*nodeMAX);

and my code do not run
Is it possible to do what I want?
thanks.

Re: Malloc a struct
 

>I want to alloc dynamically the number of nodes and also the length of s in node struct
Do it separately:

struct node *x = malloc ( nodeMAX * sizeof *x );

int i;



for ( i = 0; i < nodeMAX; i++ )

  x->s = malloc ( sMAX );

>Is it possible to do what I want?
In C89, not without invoking undefined behavior. In C99 the "struct hack" has been blessed and is directly supported as a flexible array member:

struct node{

  int a;

  char s[];

};



struct node *x = malloc ( nodeMAX * ( sizeof *x + sMAX ) );

Re: Malloc a struct
 

Also, in C, shouldn't

node *x;

be

struct node *x;

?

Another note - main returns int.

Re: Malloc a struct
 

>Also, in C, shouldn't node *x; be struct node *x; ?
Indeed. I've been working in mixed C/C++ too much these days. :icon_rolleyes: