How can a variable be used when its definition is bypassed?

Question

In my mind, always, definition means storage allocation.

In the following code, int i allocates a 4-byte (typically) storage on program stack and bind

Answer 1

The position of the declaration of i is irrelevant to the compiler. You can prove this to yourself by compiling your code with int i before the goto and then after and comparing the generated assembly:

g++ -S test_with_i_before_goto.cpp -o test1.asm
g++ -S test_with_i_after_goto.cpp -o test2.asm
diff -u test1.asm test2.asm

The only difference in this case is the source file name (.file) reference.

Answer 2

In my mind, always, definition means storage allocation.

This is not correct. The storage for the variable is reserved by the compiler when it creates the stack-layout for the function. The goto just bypasses the initialization. Since you assign a value before printing, everything is fine.