Returning pointer from a function

Question

I am trying to return pointer from a function  But I am getting segmentation fault  Someone please tell what is wrong with the code   include lt stdio h gt  int  fun    main         int  ptr      ptr fun        printf   d   ptr      int  fun         int  point       point 12        return point

User · Accepted Answer

Allocate memory before using the pointer. If you don't allocate memory *point = 12 is undefined behavior.

int *fun()
{
    int *point = malloc(sizeof *point); /* Mandatory. */
    *point=12;  
    return point;
}

Also your printf is wrong. You need to dereference (*) the pointer.

printf("%d", *ptr);
             ^

User · Answer

It is not allocating memory at assignment of value 12 to integer pointer  Therefore it crashes  because it s not finding any memory   You can try this    include lt stdio h gt   include lt stdlib h gt  int  fun     int main         int  ptr      ptr fun        printf   n t t d n   ptr      int  fun         int ptr      ptr 12      return  amp ptr

User · Answer

Although returning a pointer to a local object is bad practice  it didn t cause the kaboom here   Here s why you got a segfault   int  fun         int  point       point 12    lt  lt  lt  lt  lt  lt   your program crashed here      return point      The local pointer goes out of scope  but the real issue is dereferencing a pointer that was never initialized   What is the value of point    Who knows   If the value did not map to a valid memory location  you will get a SEGFAULT   If by luck it mapped to something valid  then you just corrupted memory by overwriting that place with your assignment to 12   Since the pointer returned was immediately used  in this case you could get away with returning a local pointer   However  it is bad practice because if that pointer was reused after another function call reused that memory in the stack  the behavior of the program would be undefined   int  fun         int point      point   12      return   amp point       or almost identically   int  fun         int point      int  point ptr      point ptr    amp point       point ptr   12      return  point ptr       Another bad practice but safer method would be to declare the integer value as a static variable  and it would then not be on the stack and would be safe from being used by another function   int  fun         static int point      int  point ptr      point ptr    amp point       point ptr   12      return  point ptr       or   int  fun         static int point      point   12      return   amp point       As others have mentioned  the  right  way to do this would be to allocate memory on the heap  via malloc

User · Answer

To my knowledge the use of the keyword new  does relatively the same thing as malloc sizeof identifier   The code below demonstrates how to use the keyword new       void main void           int  test          test   tester            printf   d   test           system  pause        return        int  tester void           int  retMe          retMe   new int    lt ----Here retMe is getting malloc for integer type          retMe   12  lt ---- Initializes retMe    Note   dereferences retMe      return retMe

[c] Returning pointer from a function

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