possible casting issues with void pointer

Question

I have no clue as to what I am doing wrong with the below code..when compiled normally this is what error I recieve

blob.c: In function ‘main’: blob.c:19:14: warning: dereferencing ‘void *’ pointer [enabled by default] blob.c:19:14: error: request for member ‘x’ in something not a structure or union

#include<stdio.h>
#include<stdlib.h>

typedef struct {

int*x;

}TIM;


main(){
    void*o;

    TIM * a;
    a=(TIM*)malloc(sizeof(TIM));
    a->x=(int*)malloc(sizeof(int));
    *(a->x)=10;
    o=(void*)a; 
    free((TIM*)o->x);

    free((TIM*)o);

}

Could someone please point me in the right direction.Hints are welcome.WHole answers if hint seems too obvious.

Hint: o->x at line 19 is invalid because o at that point is not yet of type TIM * and therefore does not have a member x — Pankrates
– Pankrates, Commented Oct 3, 2013 at 5:25

David Schwartz · Accepted Answer · 2013-10-03 05:20:42Z

2

free((TIM*)o->x);

Should be

free(((TIM*)o)->x);

answered Oct 3, 2013 at 5:20

David Schwartz

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Comments

AndersK · Accepted Answer · 2013-10-03 05:28:16Z

1

Your statement

free((TIM*)o->x);

fails because -> has higher precedence than the cast, since o is declared as void* the compiler doesn't know how to handle that.

answered Oct 3, 2013 at 5:28

AndersK

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