[MacPorts] #64694: gcc/libgcc: update older systems prior to 10.6 to a newer gcc version?

[MacPorts]

#64694: gcc/libgcc: update older systems prior to 10.6 to a newer gcc version?
----------------------------+---------------------------
  Reporter:  barracuda156   |      Owner:  (none)
      Type:  request        |     Status:  new
  Priority:  Normal         |  Milestone:
 Component:  ports          |    Version:  2.7.1
Resolution:                 |   Keywords:  leopard tiger
      Port:  libgcc, gcc10  |
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Comment (by cjones051073):

 The way things are set up for gcc in macports is a little involved,
 primarily due to the fact we want there to be a single runtime that is
 hared by all gcc compilers. This leads to slightly more complex logic in a
 number of places, than just a single version set somewhere.

 The first place to look is in the libgcc port, that is what proves the
 primary runtime. It is though just a shim port that sets a dep on a
 specific versioned libgccX based on the os versio. See

 https://github.com/macports/macports-
 ports/blob/82071e70dd05d0afd94b2d02b9801ca894eebd32/lang/libgcc/Portfile#L31

 Then, you need to look in the port files for the gcc version listed above,
 which are gcc12 for most system, and gcc7 for the really old ones.

 So, if someone wanted to migrate the old oses from using gcc7 as its
 primary runtime, to something else, you would need to first update the
 libgcc7 port, removing the logic to decide if its a primary or secondary
 runtime provider, making it a secondary for all, and move that logic into
 the gcc version you want to become the new primary runtime. See eg.

 https://github.com/macports/macports-
 ports/blob/82071e70dd05d0afd94b2d02b9801ca894eebd32/lang/gcc7/Portfile#L40

 There is probably a few other little details I have forgotten about… i
 have to remind myself how to do the migration each time i add a new major
 version, and migrate libgcc to use it.

 I am not going to do the above myself, i do not have the time but more
 importantly no means to test on OSX10.5 or older. But hopefully if someone
 else is interested the above would give them a starting point to make the
 changes ..

-- 
Ticket URL: <https://trac.macports.org/ticket/64694#comment:8>
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