[Joky]

At least for GCC/Clang this isn't what O0 means. Excerpt from the GCC manual:

> Most optimizations are completely disabled at -O0 or if an -O level is not set on the command line, even if individual optimization flags are specified.

And

> Optimize debugging experience. -Og should be the optimization level of choice for the standard edit-compile-debug cycle, offering a reasonable level of optimization while maintaining fast compilation and a good debugging experience. It is a better choice than -O0 for producing debuggable code because some compiler passes that collect debug information are disabled at -O0.

(Og isn't really implemented in clang yet, but the mindset is the same)