How to refactor old Apple SDK files displaying build warnings in C++ with OSAtomicCompareAndSwap32()?

I've got some build warnings using some older Apple SDK files, which I'm attempting to refactor to silence the warnings.
I'm confused by the syntax, and hoped someone might be able to help explain it.

An example call is
OSAtomicCompareAndSwap32(mWriteIndex, (mWriteIndex + 1) & mMask, &mWriteIndex);
Could you please help to explain (mWriteIndex + 1) & mMask ?

All arguments are defined as int32_t types.

I've tried to use std::atomic_compare_exchange_strong_explicit as described by the error message, but am getting No matching function for call using

std::atomic<int32_t> mReadIndex, mWriteIndex, mFreeIndex;

std::atomic_compare_exchange_strong_explicit(&mWriteIndex, (mWriteIndex + 1) & mMask, &mWriteIndex, std::memory_order_relaxed, std::memory_order_relaxed);

'OSAtomicCompareAndSwap32' is deprecated: first deprecated in macOS 10.12 - Use std::atomic_compare_exchange_strong_explicit(std::memory_order_relaxed)

Regarding:

(mWriteIndex + 1) & mMask

mWriteIndex + 1 is, of course, adding one to mWriteIndex.

Assuming mMask is an integer with only some number of the least-significant-bits set, then the & mMask part is an old trick to compute a modulo of (mWriteIndex + 1) without having to actually do a division/modulo operation -- e.g. if you wanted to compute x % 16, then x & 0x0F will give you the same result while potentially using fewer CPU cycles, as a bitwise-AND is traditionally faster than a divmod operation. That trick only works for doing a modulo of a power-of-two, of course.

The code you present is most likely implementing a lock-free circular FIFO queue; in this scheme the size of the circular array will always be set to a power-of-two, specifically to allow this trick to work.

Regarding the upgrading of the OSAtomicCompareAndSwap32() function call to its modern/standard-C++ replacement, I think you want something like this:

int32_t expectedVal = mWriteIndex.load();
mWriteIndex.compare_exchange_strong(expectedVal, (mWriteIndex + 1) & mMask, std::memory_order_release, std::memory_order_relaxed);