The distinction is quite clear, the reason to ever use such a flag - less so. Toolchain features are very much a popularity contest, if there is no real reason

The distinction is quite clear, the reason to ever use such a flag - less so. Toolchain features are very much a popularity contest, if there is no real reason to add a feature (and, in fact substantial reason not to), it shouldn't be implemented. The idea to use it during rapid prototyping is especially problematic, since that's the point where pernicious data access patterns will infect the entire design. Once the application "works, save from some double free bugs in weird testcases we don't expect in production, and which require a one month refactoring", the temptation to ship the flag into production will become overwhelming.