[MacPorts] #48857: gcc ports: support compiling multiple archs (universal) using the Apple GCC driver

[MacPorts]

#48857: gcc ports: support compiling multiple archs (universal) using the Apple GCC
driver
---------------------------------+-------------------------------------
 Reporter:  frederic.devernay@…  |      Owner:  macports-tickets@…
     Type:  enhancement          |     Status:  new
 Priority:  Normal               |  Milestone:
Component:  ports                |    Version:  2.3.3
 Keywords:                       |       Port:  gcc46 gcc47 gcc48 gcc49
---------------------------------+-------------------------------------
 Apple's gcc, llvm-gcc and clang have a nice feature, which is taht
 multiple archs can be specified on the same command-line (e.g. "-arch i386
 -arch x86_64").
 GNU's gcc, as installed by the gcc ports in MacPorts, doesn't have this
 feature, and thus most ports (actuall all non-muniversal ports) cannot be
 built universal using gcc.
 With the following enhancements, *all* ports could be built universal
 using a modern GNU gcc (with proper OpenMP support etc.)

 Actually, what apple did was to write a simple wrapper that calls gcc
 twice, and then lipo to merge the two objects. That driver can be compiled
 with modern gcc versions, and works very well.
 It's a single C file, called driverdriver.c, and can be found at:
 http://www.opensource.apple.com/source/gcc/gcc-5666.3/driverdriver.c?txt

 John Bower manage to modify and build that driver for GNU GCC, as
 installed by macports:
 http://thecoderslife.blogspot.fr/2015/07/building-with-gcc-46-and-
 xcode-4.html
 That blog article is about gcc 4.6, but I tested it with GCC 4.8 (built
 with +universal) and it works very well. I now have to binaries (gcc-mp
 and g++-mp) that behave exactly like Apple's GCC.

 His source code can be found at:
 https://github.com/jhnbwrs/macportsGCCfixup

 He added also building and installing configurations for Xcode, but we
 don't really need these (although that would be a bonus). The main
 improvement would be the driver.

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Ticket URL: <https://trac.macports.org/ticket/48857>
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