Macro expansion producing 'defined' has undefined behavior

[johntmcintosh]

After updating to Xcode 9.3, when building on master, I'm seeing several new build warnings related to:

macro expansion producing 'defined' has undefined behavior

A bit of stackoverflow searching seems to point to the fact that the warning is triggered by using defined outside of being inline with a #if. For example, this would throw the warning:

#define AS_KDEBUG_ENABLE defined(PROFILE) && __has_include(<sys/kdebug_signpost.h>)
#if AS_KDEBUG_ENABLE

But this would be ok:

#if defined(PROFILE) && __has_include(<sys/kdebug_signpost.h>)

However, because in this example AS_KDEBUG_ENABLE needs to be referenced from other #ifs as well, the solution is not as simple as just inlining it like above.

I'm not comfortable enough with what the macros here are doing to submit a PR with a proposed solution, but wanted to go ahead and document what's going on so that someone else hopefully can.

[alexathylane]

Dealing with same issue here. Warning is preventing us from building. :/ Looking into it soon.

[maicki]

Fixed via #879