[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 michaelld):

 OK so the build issue is these 2 lines:
 https://github.com/libusb/libusb/blob/master/libusb/os/darwin_usb.c#L2150-L2151
 {{{
   const unsigned char max_transfer_type =
 LIBUSB_TRANSFER_TYPE_BULK_STREAM;
   const char *transfer_types[max_transfer_type + 1] = {"control", "isoc",
 "bulk", "interrupt", "bulk-stream"};
 }}}
 `LIBUSB_TRANSFER_TYPE_BULK_STREAM` is part of an `enum`
 https://github.com/libusb/libusb/blob/master/libusb/libusb.h#L1098-L1113 ,
 and -could- thus be taken as a constant by the compiler. Clang indeed does
 this, but GCC at least through version 7 doesn't! The error could be more
 obvious, too ... took some sleuthing to figure out that the compiler was
 referring to the value `max_transfer_type` as being not taken as a
 constant. Luckily this issue is easily worked around via changing the 2nd
 line to:
 {{{
   const char *transfer_types[] = {"control", "isoc", "bulk", "interrupt",
 "bulk-stream", 0};
 }}}
 Either way should work, and the code makes sense either way. I just pushed
 a patch to use this latter method since it is "more correct" IMHO.

-- 
Ticket URL: <https://trac.macports.org/ticket/61868#comment:17>
MacPorts <https://www.macports.org/>
Ports system for macOS