Segmentation fault when initializing stack

Question

typedef struct stack
{
    struct stack *ptr;
    char* data; 
}*tStack;

typedef struct{
    tStack top;
}*tStack_ptr;

void Sinit(tStack_ptr s)
{
    s->top = NULL;
}

int main() {
    //stack
    tStack_ptr s;

    Sinit(s);

return 1;
}

When trying to assign top to NULL it gives me segmentation fault, any ideas? Does it have something to do with anonymous struct?

`s` is an uninitialized pointer. You have to let him point to some valid memory. — mch, Dec 09 '16 at 08:34
This can be reduced to: `struct foo { int bar; }; struct foo *ptr; ptr->bar = 42;` You're dereferencing an uninitialized pointer. — melpomene, Dec 09 '16 at 08:44

wmlhust · Answer 1 · 2016-12-09T13:32:40.887

0

tStack_ptr s;

variable 's' is just a pointer pointed to struct{tStack *top}, the system doesn't alloc any memory to a struct that it points to.

On a 32-bit PC, s takes 4 bytes in memory, same as other pointers, like 'int *'.

You can define tStack_ptr like this:

typedef struct{
    tStack top;
}tStack_ptr;

This just solve "segment fault", the sturct tStack, I am not sure what do you want.

edited Dec 09 '16 at 13:32

answered Dec 09 '16 at 10:11

wmlhust

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Segmentation fault when initializing stack

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