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

[MacPorts]

#62158: py-protobuf3: install failures: compilation error related to
PROTOBUF_MAYBE_CONSTEXPR MapFieldBase(ConstantInitialized)
---------------------+--------------------------
 Reporter:  mascguy  |      Owner:  (none)
     Type:  defect   |     Status:  new
 Priority:  Normal   |  Milestone:
Component:  ports    |    Version:
 Keywords:           |       Port:  py-protobuf3
---------------------+--------------------------
 It looks like this port is failing to install for some macOS releases,
 blocking builds for a fair number of downstream ports:

 {{{
 /usr/bin/clang -Wno-unused-result -Wsign-compare -Wunreachable-code -fno-
 common -dynamic -DNDEBUG -g -fwrapv -O3 -Wall -pipe -Os -arch x86_64
 -isysroot/ -I. -I../src
 -I/opt/local/Library/Frameworks/Python.framework/Versions/3.9/include/python3.9
 -c google/protobuf/pyext/map_container.cc -o
 build/temp.macosx-10.10-x86_64-3.9/google/protobuf/pyext/map_container.o
 -Wno-write-strings -Wno-invalid-offsetof -Wno-sign-compare -Wno-unused-
 variable -std=c++11 -Wno-shorten-64-to-32 -Wno-deprecated-register
 -stdlib=libc++  -Wno-shorten-64-to-32
 In file included from google/protobuf/pyext/map_container.cc:39:
 ../src/google/protobuf/map_field.h:332:37: error: constexpr constructor
 never produces a constant expression [-Winvalid-constexpr]
   explicit PROTOBUF_MAYBE_CONSTEXPR MapFieldBase(ConstantInitialized)
                                     ^
 ../src/google/protobuf/map_field.h:335:9: note: non-literal type
 'internal::WrappedMutex' cannot be used in a constant expression
         mutex_(GOOGLE_PROTOBUF_LINKER_INITIALIZED),
         ^
 1 error generated.
 error: command '/usr/bin/clang' failed with exit code 1
 Command failed:  cd "/opt/local/var/macports/build
 /_opt_bblocal_var_buildworker_ports_build_ports_python_py-
 protobuf3/py39-protobuf3/work/protobuf-3.14.0/python" &&
 /opt/local/Library/Frameworks/Python.framework/Versions/3.9/bin/python3.9
 setup.py --no-user-cfg --cpp_implementation install
 --prefix=/opt/local/Library/Frameworks/Python.framework/Versions/3.9
 --root=/opt/local/var/macports/build
 /_opt_bblocal_var_buildworker_ports_build_ports_python_py-
 protobuf3/py39-protobuf3/work/destroot
 Exit code: 1
 Error: Failed to destroot py39-protobuf3: command execution failed
 }}}

 Ignore the fact that this port is compiling code during phase `destroot`,
 as that's covered by issue:56534.

 These specific failures are occurring on macOS 10.10 and 10.11. Different
 compilation errors are occurring on macOS 10.8 and 10.9, which will be
 covered by a separate ticket.

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