Common reasons for bugs in release version not present in debug mode

Question

What are the typical reasons for bugs and abnormal program behavior that manifest themselves only in release compilation mode but which do not occur when in debug mode?

Answer 1

Other differences might be:

• In a garbage-collected language, the collector is usually more aggressive in release mode;
• Layout of memory may often be different;
• Memory may be initialized differently (eg could be zeroed in debug mode, or re-used more aggressively in release);
• Locals may be promoted to register values in release, which can cause issues with floating point values.