c++ - int var = 1; void main() { int i = i; }

Question

This is an interview question that I had:

int var = 1;
void main()
{
    int i = i;
}

What is the value of i after assignment? It is really compiler dependent or is it just undefined? My g++ on cygwin seems to give me 0 all the time.

Thanks

Answer 1

i has an indeterminate value because it is not initialized. So not only is it compiler dependent but it is dependent on whatever happens to be in that memory location. Variables in local scope are not initialized in C++.

I assume instead of int var = 1; at the top you meant int i = 1;.

The local scope i will still be used because the point of declaration for a variable is immediately after its declarator and before its initializer.

More specifically, Section 3.3.1-1 of the C++03 standard:

The point of declaration for a name is immediately after its complete declarator (clause 8) and before its initializer (if any), except as noted below. [Example:

int x = 12;
{ int x = x; }

Here the second x is initialized with its own (indeterminate) value. ]

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On a side note I don't think this is a very good interview question because it is related to knowing some obscure fact about the language which doesn't say anything about your coding experience.