gcc8 @8.3.0_4: build broken on Catalina or Mojave against 10.15 SDK due to unrecognized header macro __OSX_AVAILABLE_STARTING

[MaddTheSane (C.W. Betts)]

It looks like gcc8 gets confused by a few macros, such as __OSX_AVAILABLE_STARTING. Attaching a log file.

[MaddTheSane (C.W. Betts)]

Build failure log, compressed

[MaddTheSane (C.W. Betts)]

I should have mentioned this is on Catalina and Xcode 11.1.

[kencu (Ken)]

see the comments on <​https://github.com/macports/macports-ports/commit/368383b4263282656853b68965c3db455333c5bd>

somebody will need to backport that fix into gcc8 -- feeling energetic?

[sjc999]

I've a bit of a hack to fix it. The issue is that some macros are undefined - they are in /Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/usr/include/Availability.h

I'm not sure if this is a gcc or Xcode bug (the latter, I think). The #if's in Availability.h I think are wrong (not had time to really check - they are a little over the top with their nesting) but it can leave the macros undefined. In that file, near the top just after #include <AvailabilityInternal.h> add the three lines:

#define OSX_AVAILABLE_STARTING(_osx, _ios)

#define OSX_AVAILABLE_BUT_DEPRECATED(_osxIntro, _osxDep, _iosIntro, _iosDep)

#define OSX_AVAILABLE_BUT_DEPRECATED_MSG(_osxIntro, _osxDep, _iosIntro, _iosDep, _msg)

which will at least give the macros default (null) behaviour and allows gcc8 to install.

[kencu (Ken)]

the exact patch I referenced has it all sorted out. It just needs someone to backport it.

It's nobody's bug really. The Apple headers changed, and so gcc will change to support Apple's new reality.

But just use gcc9 on Catalina and you should be fine.

If nobody gets around to fixing gcc<9 on Catalina, we'll just disable them in a pre-fetch block. Probably should do that now, actually.

[cjones051073 (Chris Jones)]

Note the latest comments fro Jeremy in

​https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90835

Reads to me that this bug fell between the cracks somehow, but is being looked into now. So I would hope an Xcode update at some point might address it.

Until then, yes, it might be worth adding a pre fetch check and a useful message, if only to prevent more tickets in the meantime...

[Chris Jones <jonesc@…>]

In 481909f1dfa28ec7cad2510d3f9827bd65132d9d/macports-ports (master):

gcc{5,6,7,8}: Add pre-fetch check for Darwin19+
Closes: #59351
Closes: #59224