Creating an array of structures within another strucure in C.?

i have an assignment that involves creating a Graph ADT. within this i need to have an array of Lists.





my List ADT is basically a doubly linked list with certain functionality. to create a new you call the function:





ListRef newList();





NOTE: ListRef is defined as "typedef struct List* ListRef". i.e., its just a handle/pointer to a List structure.





the problem is that you don't know the size of the graph until run time since you create a new one with the function:





GraphRef newGraph( int n );





where n is the number of vertexes in the graph (and thus the size of the array of List ADTs) and a GraphRef is just a pointer to a Graph structure.





i'm trying to do something like this:





struct Graph{


.


.


ListRef* list_array;


.


.


}





GraphRef newGraph( int n ){


GraphRef G = malloc(sizeof(Graph));


ListRef L[n];


.


.


for( i=0; i%26lt;n; ++i){


L[i] = newList();


}


G-%26gt;list_array = L;


.


.


}





But this results in no Lists being created (they are NULL) and then a core dump. what is wrong?

Creating an array of structures within another strucure in C.?
I think that the problem is that your ListRef array is being defined on the stack in the function newGraph(int n).





Once the function scope is over, G-%26gt;list_array will be pointing to a location that it doesn't own, and the first operation that it performs on it will cause a core dump.





What you need to do instead is to create your G-%26gt;list_array using malloc:





G-%26gt;list_array = (ListRef)malloc(n*sizeof(ListRef));





and then continue as before.





Hope this helps.





P.S. Interesting problem by the way :).

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