arrays - C Pointers pointing to wrong objects -

in code, have array of 10 fraction objects, , testing purposes wanted edit first fraction in array. .h file follows:

/*frac_heap.h*/  /*typedefs*/  typedef struct {    signed char sign;    unsigned int denominator;    unsigned int numerator; }fraction;  typedef struct {     unsigned int isfree; }block;  void dump_heap(); void init_heap(); fraction* new_frac();  

in .c file following:

// file frac_heap.c #include <stdio.h> #include <stdlib.h> #include "frac_heap.h"  #define arraysize 10  fraction* heap[arraysize] = {}; block* freeblocks[arraysize] = {}; int startingblock = 0;  void init_heap(){     int x;     for(x = 0; x < arraysize; x ++){             block *currblock = &freeblocks[x];         currblock->isfree = 1;       }  } void dump_heap(){     int x;     for(x = 0; x < arraysize; x ++){         fraction* tempfrac = &heap[x];         printf("%d\t%d\t%d\n",tempfrac->sign, tempfrac->numerator, tempfrac->denominator);     }     }  fraction* new_frac(){     fraction* testfraction = &heap[0];     return testfraction; }    int main(){      init_heap();      fraction *p1;     p1 = new_frac();     p1->sign = -1;     p1->numerator  = 2;     p1->denominator = 3;     dump_heap();     return 0;    } 

the output of dump_heap() should list 10 fractions (their sign, numerator, , denominator), fraction 1 being 1 changed. however, output following:

-1  2   3 3   0   2 2   0   0 0   0   0 0   0   0 0   0   0 0   0   0 0   0   0 0   0   0 0   0   0 

how fractions 2 , 3 being edited when have pointer fraction 1 p1? using pointers wrong?

either need malloc() structures or define fixed size arrays of fraction (if size fixed.

alternative #1:

fraction heap[arraysize][10] = {}; 

alternative #2:

fraction* heap[arraysize] = {};  void init_heap(){ int x; for(x = 0; x < arraysize; x ++){         block *currblock = &freeblocks[x];     currblock->isfree = 1;        /*malloc fractions*/     heap[x] = (fraction*)malloc(  sizeof(fraction));     heap[x]->numerator=0;     heap[x]->denominator=0;     heap[x]->sign=0;     } }  void dump_heap(){     ...     fraction* tempfrac = heap[x]; /*you cannot de-reference heap*/     ... }  fraction* new_frac(){     ...     fraction* testfraction = heap[0];     ... }