[MacPorts] #33429: python27 @2.7.2_4 subports fail to build when compiler path changes

[MacPorts]

#33429: python27 @2.7.2_4 subports fail to build when compiler path changes
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 Reporter:  benoit.triquet@…          |       Owner:  macports-tickets@…                   
     Type:  defect                    |      Status:  new                                  
 Priority:  Normal                    |   Milestone:                                       
Component:  ports                     |     Version:  2.0.4                                
 Keywords:                            |        Port:  python27                             
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 python27 records the compiler path when built and that path is later used
 to build modules such as py27-tkinter, which fails if the compiler changes
 locations such as with the transition from Xcode 4.1 to Xcode 4.3

 A work-around is to force a rebuild of python without dependent rebuilds:
 {{{
 port -n upgrade --force python27
 }}}

 Suggestions of solutions:
 1) have the perl and python portgroups check that the compiler hardcoded
    into the interpreter is still available, and tell the user to
    rebuild as necessary
 2) make perl/python/etc modules build using ${configure.compiler}
    instead of the compiler used by the interpreter.

 (1) is more a work-around than a fix (i don't know the rules of macports
 but i believe interactions shall be forbidden) but should be otherwise
 harmless.
 (2) may fail to guarantee that the newly found compiler is link- and abi-
 compatible with the previous one, so it's not clear that this solution is
 fine. Then again, it's not clear that a new compiler found at the recorded
 solution, as would be silently accepted in the current implementation of
 python27, is fine either.

 PS: thanks to Dan Ports for identifying my problem and providing the above
 work-around and suggestions. Dan says that other python versions may be
 affected as well as perl5, apr and postgresql.

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Ticket URL: <https://trac.macports.org/ticket/33429>
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