[MacPorts] #62158: py-protobuf3: install failures for macOS 10.8 through 10.11: compilation error related to PROTOBUF_MAYBE_CONSTEXPR MapFieldBase(ConstantInitialized)

[MacPorts]

#62158: py-protobuf3: install failures for macOS 10.8 through 10.11: compilation
error related to PROTOBUF_MAYBE_CONSTEXPR MapFieldBase(ConstantInitialized)
---------------------------+-------------------------
  Reporter:  mascguy       |      Owner:  Schamschula
      Type:  defect        |     Status:  assigned
  Priority:  Normal        |  Milestone:
 Component:  ports         |    Version:
Resolution:                |   Keywords:
      Port:  py-protobuf3  |
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Comment (by Schamschula):

 So I update a port to the current upstream release version, which builds
 correctly on my build machine (Mojave). I push the update, only to find
 out later that El Capitan and below have an issue.

 If you want to run older macOS versions, you are likely to run into this
 type of issue. Upstream developers, in this case Google, often only
 support the latest OS versions, breaking backwards compatibility.

 Making things work on older systems takes a bit of detective work, which
 requires access to a machine running the older OS.  I don't have a machine
 running anything below Mojave. The only possible way for me to test on
 older systems is to blindly throw possible fixes at the CI systems.

 Of course we're also running into the opposite problem: very old packages
 need a lot of updates to run on new systems, e.g. the arm64 platform.

-- 
Ticket URL: <https://trac.macports.org/ticket/62158#comment:7>
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