Clang not reporting uninitalized variables in C++?
- Why not the warning?
Using clang with -Wall on my system correctly warns about the error. Apparently, the default settings do not include -Wall (may be to avoid generating warnings with correct code that was written before some of the warnings were introduced).
In general, you're however going to be in trouble if you rely on the compiler to help you with sloppy programming. Typing in code without thinking carefully and hoping the compiler will tell you all mistakes is bad in any language but a true total disaster with C++. The main philosophy of C++ is simply that the programmer doesn't make any error, so just don't make them ;-)
Think carefully and also always work with -Wall if you can.
- Why is initialized?
Apparently, you've not understood what is the meaning of "undefined behavior". It doesn't mean the program crashes, it doesn't mean it will do anything funny. It means it can do anything and normally the programs do whatever will create the most problems for you in the future.
Often this most dangerous behavior is to make it look as if everything is fine (e.g. that your variable is indeed initialized). The bad values will only show once you put that code in production or only when you show your program running in front of a vast audience. At that point, the value will be different and the video of your public crash will go viral on youtube, your wife will change the door locks and even your parents will not answer your phone calls.
Just initialize your variables; it's better :-)