[MacPorts] #55471: Use separate portindexes for libc++ on older systems

[MacPorts]

#55471: Use separate portindexes for libc++ on older systems
--------------------------+----------------------------
  Reporter:  ryandesign   |      Owner:  neverpanic
      Type:  enhancement  |     Status:  assigned
  Priority:  Normal       |  Milestone:  MacPorts 2.5.0
 Component:  base         |    Version:
Resolution:               |   Keywords:
      Port:               |
--------------------------+----------------------------

Comment (by mojca):

 Still, when I run
 {{{
 portindex -p macosx_12_i386 -o PortIndex.12_i386
 }}}
 on a file containing
 {{{
 subport
 foo-${os.platform}-${os.major}-${configure.cxx_stdlib}-${cxx_stdlib} {}
 }}}
 then I get
 {{{
 Adding subport foo-darwin-12-libc++-libc++
 }}}
 so either I did not patch my MacPorts correctly (which is quite possible)
 or the code does not set/use the correct stdlib.

 One thing that still slightly bothers me (but I would not worry about it
 yet) is that we would sometimes need a conditional like
 {{{
 #!tcl
 if {c++11 is supported} {
     version 1.2
 } else {
     version 0.9
 }
 }}}
 Making the decision based on stdlib alone will not work correctly on, say,
 10.5/ppc/gcc7 configuration, nor with cxx11 1.1 PortGroup on
 10.8/libstdc++.

 Lower priority though, nothing to worry about at this very moment.

 But I would like to know whether you can reproduce the above behaviour or
 not.

--
Ticket URL: <https://trac.macports.org/ticket/55471#comment:14>
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