Cleanups 3: Simple changes

[Stephan T. Lavavej (StephanTLavavej)]

• : Fuse #if !_HAS_CXX20 sections.
• : wbuffer_convert and wstring_convert were using implicit private:.
• : scoped_allocator_adaptor was using implicit private:.
• : Remove repeated protected:.
• : Mark _Small_object_num_ptrs as _INLINE_VAR.
• : Mark constants as _INLINE_VAR.
  • We conventionally mark constants as _INLINE_VAR (or inline in C++17+) even when there's no real risk of odr-using them.
• : Use _STL_INTERNAL_STATIC_ASSERT for _Big_allocation_alignment.
  • This is a constant that we control, so there's no reason to evaluate these static_asserts for user code.
• : Mark _Future_error_map as _NODISCARD.
• : Extract _Array_const_iterator members that are IDL-independent.
  • This reduces repetition, and will make it easier to move n + iter to be a hidden friend (currently blocked by a compiler bug until 17.3 Preview 2).
• Avoid various uses of auto*.

[nicole mazzuca (strega-nil-ms)]

• Should this also change VSO_0{7}_initialize_everything:test_weak_ptr_construction:all_zero to remove auto*?

[Stephan T. Lavavej (StephanTLavavej)]

nicole mazzuca (@strega-nil-ms) - good question. This is creating a templated lambda:

STL/tests/std/tests/VSO_0000000_initialize_everything/test.cpp

Lines 323 to 327 in 314f65f

	const auto all_zero = [](const auto* const ptr) {
	const auto first = reinterpret_cast<const char*>(ptr);
	const auto last = reinterpret_cast<const char*>(ptr + 1);
	return all_of(first, last, [](const auto x) { return x == 0; });
	};

I initially hesitated to change this because it seemed a larger change than the rest, but you're right, eliminating the last occurrence of auto* seems worth it. It's OK if ptr ends up being a const pointer to modifiable T (I didn't look into the usage deeply enough to see whether that actually happens), as we add constness when reinterpreting to const char* and don't otherwise interact with ptr.

[Stephan T. Lavavej (StephanTLavavej)]

I'm mirroring this to the MSVC-internal repo - please notify me if any further changes are pushed.