C programming Language placement problem with solution

1)

 Is there any difference between the two declarations, 

1. int foo(int *arr[]) and

2. int foo(int *arr[2])

Answer:

No 

Explanation:

Functions can only pass pointers and not arrays. The numbers that are allowed inside the [ ] is just for more readability. So there is no difference between the two declarations.

2)

What is the subtle error in the following code segment?

void fun(int n, int arr[])

{

int *p=0;

int i=0;

while(i++

p = &arr[i];

*p = 0;

}

Answer & Explanation:-

If the body of the loop never executes p is assigned no address. So p remains NULL where *p =0 may result in problem (may rise to runtime error “NULL pointer assignment” and terminate the program).     

3)

What is wrong with the following code?  

int *foo()

{

int *s = malloc(sizeof(int)100);

assert(s != NULL);

return s;

}

Answer & Explanation:-

assert macro should be used for debugging and finding out bugs. The check s != NULL is for error/exception handling and for that assert shouldn’t be used. A plain if and the corresponding remedy statement has to be given.

4)

What is the hidden bug with the following  statement?

assert(val++ != 0);

Answer & Explanation:-

Assert macro is used for debugging and removed in release version. In assert, the experssion involves side-effects. So the behavior of the code becomes different in case of debug version and the release version thus leading to a subtle bug. 

Rule to Remember:

Don’t use expressions that have side-effects in assert statements.  

5)

void main()

{

int *i = 0x400;  // i points to the address 400

*i = 0; // set the value of memory location pointed by i;

}

Answer:

Undefined behavior 

Explanation:-

The second statement results in undefined behavior because it points to some location whose value may not be available for modification.  This type of pointer in which the non-availability of the implementation of the referenced location is known as 'incomplete type'.