QT Problems on macOS 15

[Fred Wright]

On Wed, 4 Sep 2024, Mark E Anderson wrote:

> Side note - Fred, can you send me some ports where I can find the Float16 bug?

I don't know of any specific *ports* (yet), since I found this in some 
legacy-support testing involving trying all possible combinations of OS 
(with the associated Xcode compiler) and SDK.  The conditions for failure 
are:

1) Using the macOS 15 SDK.

2) Using the math.h header.

3) Using any compiler that doesn't implement the _Float16 type.

I didn't keep track of which OS/compiler cases are too old for _Float16, 
though I could investigate that if needed.  My guess is that at least some 
MacPorts compilers are sufficiently old for #3, so you don't necessarily 
need an old OS install.  Requirements #1 and #2 are trivial to create.

Apple typically tries to provide fallbacks for older compilers, though 
they don't always get it right.  This case can't just be a dummy macro 
definition, though conditionaling out the entire set of declarations would 
work.  I don't know if there's a way to directly test for _Float16 support 
in a preproccessor conditional, or whether it would have to be yet another 
kludge that tests for specific clang versions or specific gcc versions.

Fred Wright