+10  A: 

Different compilers do different things. The standard doesn't state that all variables should be initialized automatically, so many compilers don't. This means they are typically filled with garbage. Sometimes you luck out and get a block of zeros, but it's rare. Don't count on it.

JoshD  2010-10-08 23:49:54
Always, always, always initialize variables. Then, even if your code is incorrect, at least it is also consistent.
John Gaughan  2010-10-09 00:08:10
Initialize variables! Your life may depend on it.
karlphillip  2010-10-09 00:09:21
@yan The standard doesn't state that it must be random either.
PigBen  2010-10-09 00:16:26
@yan: It's a good practice to initialize all variables from the start.
Throwback1986  2010-10-09 00:44:56
@yan What kind of abnormal behavior do you imagine an uninitialized variable could actually help you detect? I can't think of a case where using the value of an uninitialized variable wouldn't be a problem in its own right and in need of being solved before anything else useful could be accomplished with it.
TheUndeadFish  2010-10-09 00:45:24
yan bellavance  2010-10-09 00:50:09
@yan bellavance: I didn't say anything about random events. I said some compilers will initialize some things, others won't. Don't be misled by that block of zeros comment.
JoshD  2010-10-09 00:50:40

related questions

Of Memory Management, Heap Corruption, and C++
How do I make a GUI?
Alpha blending sprites in Nintendo DS Homebrew
Thread safe lazy contruction of a singleton in C++
Interview Programming Questions - In house Exam
Link issues (VC6)
What are the barriers to understanding pointers and what can be done to overcome them?
Why are professors or schools picking Java over C++ to teach to students?
What is the best way to create a sparse array in C++
C/C++ library for reading MIDI signals from a USB MIDI device
How do you pack a visual studio c++ project for release?
How to set up unit testing for Visual Studio C++
How do I configure and communicate with a serial port?
Lightweight IDE for Linux
Mapping Stream data to data structures in C#
CPU throttling in C++
Asynchronous multi-direction server-client communication over the same open socket?
Exceptions in C++
Heap corruption under Win32; how to locate?
Build for Windows NT 4.0 using Visual Studio 2005?
C++: Should I use nested classes in this case?
BerkeleyDB Concurrency
GTK implementation of MessageBox
Is gettimeofday() guaranteed to be of microsecond resolution?
How to use the C socket API in C++ on z/OS