[C++] Undefined Behavior, UB

C++ Undefined Behavior - what is it, and why should I care?

• Signed integer overflow (but not unsigned!)
• Dereferencing NULL pointer or result of malloc(0) // 0 point to virtual memory 0 position. Also a reason why program start memory not 0.
• Shift greater than (or equal to) the width of the operand
• Reading from uninitialized variables
• Modifying a variable more than once in an expression : Sequence point
• Buffer overflow
• Comparing pointers into two different data structures
• Pointer overflow : GCC and pointer overflows
• Modifying a const object (C++) or a string literal
• Negating INT_MIN  : Why does -INT_MIN = INT_MIN in a signed, two's complement representation?
• Data races
• Mismatch between new and delete
• Calling a library routine w/o fulfilling the prerequisites
• memcpy with overlapping buffers // copy/copy_if , The source and destination ranges cannot overlap.
• atomic_is_lock_free requires passing in obj shall not be nullptr
• If during the evaluation of an expression, the result is not mathematically defined or not in the range of representable values for its type, the behavior is undefined.

clang -fsanitize=undefined

A Guide to Undefined Behavior in C and C++, Part 1

A Guide to Undefined Behavior in C and C++, Part 2

A Guide to Undefined Behavior in C and C++, Part 3

Contest: Craziest Compiler Output due to Undefined Behavior
Undefined Behavior Consequences Contest Winners

What Every C Programmer Should Know About Undefined Behavior #1/3
What Every C Programmer Should Know About Undefined Behavior #2/3
What Every C Programmer Should Know About Undefined Behavior #3/3


Marshall's C++ Musings