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Is the following code undefined behavior, implementation defined or defined by the standard? I couldn't find any reference regarding assigning an integer to its own address.
volatile int x = (int)&x; This code gets translated to:
lea eax,[ebp-4] mov dword ptr [ebp-4],eax 
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You need to initialize a pointer by assigning it a valid address. This is normally done via the address-of operator (&). The address-of operator (&) operates on a variable, and returns the address of the variable. For example, if number is an int variable, &number returns the address of the variable number.
An address is a type of pointer value, but pointer values don't point at values; they point at objects or functions.
You can print a pointer value using printf with the %p format specifier. To do so, you should convert the pointer to type void * first using a cast (see below for void * pointers), although on machines that don't have different representations for different pointer types, this may not be necessary.
In C, using x in both the declaration and the initialization is fine:
(C99, 6.2.1p7) "[...] Any other identifier has scope that begins just after the completion of its declarator."
The result of the conversion of the pointer to the integer is implementation-defined and can be undefined behavior:
(C99, 6.3.2.3p7) "Any pointer type may be converted to an integer type. Except as previously specified, the result is implementation-defined. If the result cannot be represented in the integer type, the behavior is undefined. The result need not be in the range of values of any integer type."
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