> in gdb, it prints many variable values as "optimized out". This is because your contract with the C/C++ compiler is not "produce machine instructions that fa

> in gdb, it prints many variable values as "optimized out". This is because your contract with the C/C++ compiler is not "produce machine instructions that faithfully implement the program as written", but "produce machine instructions that have the same side-effects as the program". Anything that is not explicitly marked as observable (and whose state is thus a side-effect) is fair game. Arguments passed to functions out of scope (remember LTO...), memory same, volatile-qualified storage... that's about it. Debuggability of an optimised program is an accident, not an objective.