[MacPorts] #48471: FSF gcc48 fails to compile projects on El Capitan due to OS X SDK bug in Availability.h

[MacPorts]

#48471: FSF gcc48 fails to compile projects on El Capitan due to OS X SDK bug in
Availability.h
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  Reporter:  jasonw@…  |      Owner:  mww@…
      Type:  defect    |     Status:  new
  Priority:  Normal    |  Milestone:
 Component:  ports     |    Version:  2.3.3
Resolution:            |   Keywords:  elcapitan
      Port:  gcc48     |
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Comment (by murrayeisenberg@…):

 Replying to [comment:50 ryandesign@…]:
 > Replying to [comment:48 murrayeisenberg@…]:
 > > Replying to [comment:41 jeremyhu@…]:
 > > > Yes.  If you want, you can just manually edit Availability.h to
 replace the '`defined(__has_feature)`' with '`defined(__has_attribute)`'
 for the OSX and iOS availability macros, but you do so at your own risk
 because you know what you're doing ;)
 > >
 > > Even using {{{sudo}}} with an admin account on OS X 10.11.1 did not
 allow me to edit Availability.h. How did you do it (if you did)?
 >
 > System Integrity Protection (SIP), a new feature as of OS X 10.11 El
 Capitan, will not allow you to edit files in system locations like /usr.
 SIP can be turned off, but I recommend you don't do that.
 >
 > > Also, I could not even build gcc48, again apparently due to the same
 issue with Availability.h.
 >
 > Yes.

 Yes, I know about SIP and how to turn it on and off, but for the obvious
 reasons hesitate to do so. So:
  (1) Is there to be some other workaround?
 (2) In case I dare to turn off SIP temporarily...

 Is it literally just the several instances of {{{ 'defined(__has_feature)'
 }}} that have to be replaced?  I ask because in Availability.h there are
 other mentions of "availability", such as in
 {{{'#if __has_feature(attribute_availability_*)'}}} where what follows
 {{{'availability'}}} could be {{{'twos'}}}, {{{'watchOS'}}},
 {{{'app_extension'}}}, etc.

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Ticket URL: <https://trac.macports.org/ticket/48471#comment:51>
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