[nwlieb]

There's some ambiguity for argument destruction order for example: https://stackoverflow.com/a/36992250

Similarly, the construction/destruction order for std::tuple elements is not well defined.

Granted, that's implementation defined behavior, which is technically deterministic on a single compiler.

[jstimpfle]

This isn't really about constructors/destructors. Expressions like function calls with multiple arguments have always been "unsequenced" with respect to each other. In other words the order is left to decide for the compiler. It's always been like that, going back to C (and probably other languages). If you call f(x++, x++) what values get passed to f is unspecified.

I suppose the destruction of whatever the expressions constructed still happens in reverse order of construction.

But either way I might not even care, I'm aware that at the level of a single statement the execution sequences aren't much defined, so I rarely put more than one mutating thing per expression, or otherwise I'm sure that I don't care about the order -- I could live with any sequence as well as totally parallel execution.

Example: buf[i++] = 5 has 2 mutating sub-expressions, but I know it's not messing up anything. I don't care whether i gets incremented before 5 gets assigned or the other way around.