A local non-static variable of a non-class type has an undefined value before it is initialized. For example, it is incorrect to rely on an uninitialized integer to have the value 0.

Review the code and consider whether the variable should have an initializer or whether some path through the program lacks an assignment to the variable.

The function absWrong does not initialize the variable j in the case where i = 0. Functions absCorrect1 and absCorrect2 remedy this deficiency by adding an initializer and adding an assignment to one of the paths through the program, respectively.

ISO/IEC 9899:2011: Programming languages - C (Section 6.3.2.1).