Various ways to swap two variables without using a temporary variable

The normal way of doing a simple swap is as follows.
int a,b,t;
t = a;
a = b;
b = t;
But this can be done in different methods with out using an extra or temporary variable but each  method has its own flaws.

Method1 (The XOR trick)

a ^= b ^= a ^= b;
Although the code above works fine for most of the cases, it tries to modify variable 'a' two times between sequence points, so the behavior
is undefined. What this means is it wont work in all the cases. . Also, think of a scenario
where you have written your code like this
swap(int *a, int *b)
{
*a ^= *b ^= *a ^= *b;
}
Now, if suppose, by mistake, your code passes the pointer to the same variable to this function. Guess what happens? Since Xor'ing an
element with itself sets the variable to zero, this routine will end up setting the variable to zero (ideally it should have swapped the
variable with itself). This scenario is quite possible in sorting algorithms which sometimes try to swap a variable with itself (maybe due to
some small, but not so fatal coding error). One solution to this problem is to check if the numbers to be swapped are already equal to each
other.
swap(int *a, int *b)
{
if(*a!=*b)
{
*a ^= *b ^= *a ^= *b;
}
}

Method2(using + and - )

This method is also quite popular
a=a+b;
b=a-b;
a=a-b;
But, note that here also, if a and b are big and their addition is bigger than the size of an int, even this might end up giving you wrong
results.
Method3(using macro)
One can also swap two variables using a macro. However, it would be required to pass the type of the variable to the macro. Also, there is
an interesting problem using macros. Suppose you have a swap macro which looks something like this
#define swap(type,a,b) type temp;temp=a;a=b;b=temp;
Now, think what happens if you pass in something like this
swap(int,temp,a) //You have a variable called "temp" (which is quite possible).
This is how it gets replaced by the macro
int temp;
temp=temp;
temp=b;
b=temp;
Which means it sets the value of "b" to both the variables!. It never swapped them! Scary, isn't it?
Conclusion:
 Use a temporary variable. Its not only fool proof, but also easier to understand and maintain as trying to do something tricky will have some or the other loopholes which are very difficult to identify at the first glance.