Can You Initialize a Variable Using Itself in C/C ?

When is it Acceptable to Use a Newly Declared Variable in Its Initialization?

The unusual syntax of initializing a variable using itself, as in int x = x 1;, has left many programmers baffled. While it may intuitively seem incorrect, understanding the underlying mechanics behind this behavior sheds light on its purpose and limitations.

In C/C , variables come into existence at the assignment operator (the = sign). This means that in the expression int x = x 1;, the variable x is declared and comes into scope before its value is initialized. This allows you to use x on the right-hand side of the assignment.

However, it's crucial to remember that the value of x at this point is indeterminate. This behavior is undefined unless you're initializing a variable with static storage duration (e.g., outside of a function).

According to C 03, the point of declaration for a name is immediately after its complete declarator and before its initializer. This means that the second x in the example below is initialized with its indeterminate value:

<code class="c++">int x = 12;
{ int x = x; }</code>

Understanding this nuanced behavior is essential for writing correct and optimized code. While using a newly declared variable in its initialization may be valid in certain scenarios, it's advisable to avoid this practice unless the implications of indeterminate values are fully understood.

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