[libcxx-commits] [libcxx] [libc++] Default the allocator argument for most string constructors (PR #169901)

[David Spickett via libcxx-commits]

DavidSpickett wrote:

Changing the optimisation level causes a random selection of tests to pass/unexpected pass but in all cases size_size_string_size_size.pass.cpp still does not fit. If it's exception information I suppose this makes sense, you can make the code path as small or as fast as you want but it still has to know how to handle the exceptions.

That some tests change result is not a good sign but also not relevant to this PR. As the test will be run in the no-exceptions build anyway, I suggest you add this to it:
```
// The machine emulated in tests does not have enough memory for code.
// UNSUPPORTED: LIBCXX-PICOLIBC-FIXME && !no-exceptions
```

And I will look into the weird results when changing the options. Many are using atomics, which I'm not sure we even have on Cortex-M. So enabling optimisations may remove calls that would otherwise fail. Maybe I can prevent that.

https://github.com/llvm/llvm-project/pull/169901