[MacPorts] #71823: Port installs useless llvm-17 and clang-17 over and over again on macOS High Sierra, version 10.13.6

[MacPorts]

#71823: Port installs useless llvm-17 and clang-17 over and over again on macOS
High Sierra, version 10.13.6
------------------------+------------------------
  Reporter:  ballapete  |      Owner:  (none)
      Type:  defect     |     Status:  new
  Priority:  Normal     |  Milestone:
 Component:  ports      |    Version:  2.10.5
Resolution:             |   Keywords:  highsierra
      Port:  llvm-17    |
------------------------+------------------------

Comment (by ryandesign):

 Replying to [comment:5 ballapete]:
 > {{{
 > root 263 /\ port echo installed and 'depends::llvm-19(\s|$)'
 > mesa                           @24.3.2_0+llvm
 > }}}
 >
 > needs `llvm-19` but has `set llvm_ver            17` in its `Portfile`?

 No, the mesa Portfile has said `set llvm_ver 19` ever since
 [changeset:700867fa87e7ccf14f457dda3bd5a99e3ff593d5/macports-ports the
 +llvm variant was added to the port in December]. If yours says `set
 llvm_ver 17` then you must have edited it to say that.

 mesa requires C++17, so if your Xcode compiler is not sufficient, it will
 use whatever compiler MacPorts chooses to use to compile C++17 code.

 In addition, when the +llvm variant is selected, which it is by default
 unless you are on Mac OS X 10.6 or earlier, it will build the llvmpipe
 driver, which uses llvm-19. If you do not want this driver and its llvm-19
 dependency you can deselect the llvm variant.

 Looking at a few other ports you mentioned,
 [changeset:fc997b471983eb6869d3d8f77dd87fa9e3b2e080/macports-ports the
 highway port specifically blacklists Xcode clang < 1001] because it didn't
 build with those older clangs. The newest Xcode clang available on macOS
 10.13 is 1000, so yes, MacPorts will choose a newer MacPorts clang to
 build that port.

 fswatch, like mesa, specifies that it needs a C++17 compiler.
 CompilerSelection says MacPorts wants Xcode clang 1000.11.45.2 or newer
 for C++17 support. If you have Xcode 10 on macOS 10.13 you have this
 compiler version but if you have Xcode 9 then you don't and MacPorts will
 pick a newer MacPorts clang compiler. Per source:macports-
 ports/_resources/port1.0/compilers/clang_compilers.tcl MacPorts doesn't
 offer MacPorts clang versions greater than 17 to macOS versions under 13
 because of #68640.

-- 
Ticket URL: <https://trac.macports.org/ticket/71823#comment:6>
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