openimageio @2.1.20 does not build with openvdb @11.0.0 due to conflicting headers: error: 'IMATH_CONSTEXPR14' does not name a type; did you mean 'OIIO_CONSTEXPR14'?

[barracuda156]

openvdb depends on openexr (v. 3), while openimageio depends on openexr2. These do not work together:

[ 64%] Building CXX object src/libOpenImageIO/CMakeFiles/OpenImageIO.dir/__/pnm.imageio/pnminput.cpp.o
cd /opt/local/var/macports/build/_opt_PPCSnowLeopardPorts_graphics_openimageio/openimageio/work/build/src/libOpenImageIO && /opt/local/bin/g++-mp-13 -DEMBED_PLUGINS=1 -DOpenImageIO_EXPORTS -DUSE_BOOST_ASIO=1 -DUSE_DCMTK=1 -DUSE_FFMPEG -DUSE_FIELD3D=1 -DUSE_FREETYPE=1 -DUSE_GIF -DUSE_HEIF=1 -DUSE_JPEG_TURBO=1 -DUSE_LIBRAW=1 -DUSE_OCIO=1 -DUSE_OPENCOLORIO=1 -DUSE_OPENJPEG -DUSE_OPENVDB=1 -DUSE_PTEX -DUSE_STD_REGEX -DUSE_TBB=1 -DUSE_WEBP=1 -D__STDC_CONSTANT_MACROS -D__STDC_LIMIT_MACROS -I/opt/local/var/macports/build/_opt_PPCSnowLeopardPorts_graphics_openimageio/openimageio/work/build/include -I/opt/local/var/macports/build/_opt_PPCSnowLeopardPorts_graphics_openimageio/openimageio/work/build/src/include -I/opt/local/var/macports/build/_opt_PPCSnowLeopardPorts_graphics_openimageio/openimageio/work/OpenImageIO-2.1.20.0/src/include -I/opt/local/libexec/openexr2/include -I/opt/local/libexec/openexr2/include/OpenEXR -I/opt/local/include/libfmt9 -I/opt/local/include/openjpeg-2.5 -I/opt/local/libexec/tbb/include -I/opt/local/include/freetype2 -isystem /opt/local/libexec/boost/1.76/include -isystem /opt/local/include -pipe -I/opt/local/libexec/boost/1.76/include -Os -Wno-deprecated-declarations -Wno-unknown-warning-option -DNDEBUG -I/opt/local/libexec/boost/1.76/include -I/opt/local/include -D_GLIBCXX_USE_CXX11_ABI=0 -std=c++17 -arch ppc -mmacosx-version-min=10.6 -fPIC -Wno-unused-local-typedefs -Wno-unused-result -Wno-aligned-new -Wno-noexcept-type -fno-math-errno -MD -MT src/libOpenImageIO/CMakeFiles/OpenImageIO.dir/__/pnm.imageio/pnminput.cpp.o -MF CMakeFiles/OpenImageIO.dir/__/pnm.imageio/pnminput.cpp.o.d -o CMakeFiles/OpenImageIO.dir/__/pnm.imageio/pnminput.cpp.o -c /opt/local/var/macports/build/_opt_PPCSnowLeopardPorts_graphics_openimageio/openimageio/work/OpenImageIO-2.1.20.0/src/pnm.imageio/pnminput.cpp
In file included from /opt/local/include/openvdb/Types.h:13,
                 from /opt/local/include/openvdb/openvdb.h:8,
                 from /opt/local/var/macports/build/_opt_PPCSnowLeopardPorts_graphics_openimageio/openimageio/work/OpenImageIO-2.1.20.0/src/openvdb.imageio/openvdbinput.cpp:15:
/opt/local/include/Imath/half.h:579:5: error: 'IMATH_CONSTEXPR14' does not name a type; did you mean 'OIIO_CONSTEXPR14'?
  579 |     IMATH_CONSTEXPR14 half round (unsigned int n) const IMATH_NOEXCEPT;
      |     ^~~~~~~~~~~~~~~~~
      |     OIIO_CONSTEXPR14
/opt/local/include/Imath/half.h:632:5: error: 'IMATH_CONSTEXPR14' does not name a type; did you mean 'OIIO_CONSTEXPR14'?
  632 |     IMATH_CONSTEXPR14 void setBits (uint16_t bits) IMATH_NOEXCEPT;
      |     ^~~~~~~~~~~~~~~~~
      |     OIIO_CONSTEXPR14
/opt/local/include/Imath/half.h:678:8: error: 'IMATH_CONSTEXPR14' does not name a type; did you mean 'OIIO_CONSTEXPR14'?
  678 | inline IMATH_CONSTEXPR14 half
      |        ^~~~~~~~~~~~~~~~~
      |        OIIO_CONSTEXPR14
/opt/local/include/Imath/half.h:888:8: error: 'IMATH_CONSTEXPR14' does not name a type; did you mean 'OIIO_CONSTEXPR14'?
  888 | inline IMATH_CONSTEXPR14 void
      |        ^~~~~~~~~~~~~~~~~
      |        OIIO_CONSTEXPR14

See also: ​https://bugs.gentoo.org/832862