[MacPorts] #61868: libusb @1.0.24: cannot parse USB.h with mainline gcc versions due to variant pragma handling not accepted by gcc

[MacPorts]

#61868: libusb @1.0.24: cannot parse USB.h with mainline gcc versions due to
variant pragma handling not accepted by gcc
-----------------------------------+-----------------------
  Reporter:  dgonyier              |      Owner:  michaelld
      Type:  defect                |     Status:  reopened
  Priority:  Normal                |  Milestone:
 Component:  ports                 |    Version:  2.6.4
Resolution:                        |   Keywords:
      Port:  libusb, libusb-devel  |
-----------------------------------+-----------------------

Comment (by fhgwright):

 Just to add to the confusion, I came across this GCC documentation (for
 GCC 6), from Fedora of all places:

 [https://dmalcolm.fedorapeople.org/gcc/2015-08-31/rst-experiment/pragmas-
 accepted-by-gcc.html#darwin-pragmas]

 This claims that the relevant pragma is accepted when GCC is built for
 Darwin.  Does this documentation lie, or are MacPorts GCCs missing some
 configure option to enable Darwin-related features?

 BTW, the pragma is present in all OS versions 10.4-10.13 (at least), and
 no MacPorts GCC accepts it.

 A couple of other notes:

 Configure fails on 10.4, because libusb requires thread-local storage, but
 the compiler setup doesn't specify that.

 There's some clang blacklisting claiming to be related to `stdatomic.h`,
 but `stdatomic.h` doesn't appear in the libusb sources at all.

-- 
Ticket URL: <https://trac.macports.org/ticket/61868#comment:43>
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