Your compiler is your friend. If it issues a warning for a certain construct, often there's a potential problem in your code.
Successful builds should be silent (warning-free). If they aren't, you'll quickly get into the habit of skimming the output, and you will miss real problems. (See Item 2.)
To get rid of a warning: a) understand it; and then b) rephrase your code to eliminate the warning and make it clearer to both humans and compilers that the code does what you intended.
Do this even when the program seemed to run correctly in the first place. Do this even when you are positive that the warning is benign. Even benign warnings can obscure later warnings pointing to real dangers.