On Wednesday, 13 November 2013 at 00:33:17 UTC, Andrei
Alexandrescu wrote:
For starters, I want to define a function that "obliterates" an
object, i.e. makes it almost surely unusable and not obeying
its own invariants. At the same time, that state should be
entirely reproducible and memory-safe.
What's this for? When will it be used?
How will it behave in release mode? No-op, or same as non-release?
Here's what I'm thinking. First, obliterate calls the
destructor if present and then writes the fields as follows:
* unsigned integers: t.max / 2
* signed integers: t.min / 2
* characters: ?
Why not 0xFF? (char.init, invalid UTF-8 code unit)
* Pointers and class references: size_t.max - 65_535, i.e. 64K
below the upper memory limit. On all systems I know it can be
safely assumed that that area will cause GPF when accessed.
Make that value odd. That will also guarantee a GPF on systems
where unaligned pointer access is forbidden.
* Arrays: some weird length (like 17), and also starting at
size_t.max minus the memory occupied by the array.
I guess the non-zero length is for code which is going to check
it? Because otherwise, leaving length as just 0 will, in debug
mode, cause a range error. In release mode, array index access
will not check the length anyway.
* floating point numbers: NaN, or some ridiculous value like
F.max / 2?
NaNs are viral, so there's that.
