FTBFS w/ Clang on MSYS2

[kmilos]

OpenEXR 3.3.5 fails to build against Imath 3.2.1 using Clang (20.1.8) on MSYS2 (CLANG64 or CLANGARM64 environments):

FAILED: [code=1] src/lib/OpenEXR/CMakeFiles/OpenEXR.dir/ImfBoxAttribute.cpp.obj 
  D:\M\msys64\clang64\bin\clang++.exe -DIMATH_DLL -DOPENEXR_DLL -DOPENEXR_EXPORTS -DOpenEXR_EXPORTS -ID:/_/B/src/build-CLANG64/src/lib/OpenEXR -ID:/_/B/src/openexr-3.3.5/src/lib/OpenEXR -ID:/_/B/src/build-CLANG64/cmake -ID:/_/B/src/openexr-3.3.5/src/lib/Iex -ID:/_/B/src/openexr-3.3.5/src/lib/IlmThread -ID:/_/B/src/openexr-3.3.5/src/lib/OpenEXRCore -isystem D:/M/msys64/clang64/include/Imath -march=nocona -msahf -mtune=generic -O2 -pipe -Wp,-D_FORTIFY_SOURCE=2 -fstack-protector-strong -Wp,-D__USE_MINGW_ANSI_STDIO=1 -Wno-ignored-attributes -O3 -DNDEBUG -fvisibility=hidden -fvisibility-inlines-hidden -pthread -MD -MT src/lib/OpenEXR/CMakeFiles/OpenEXR.dir/ImfBoxAttribute.cpp.obj -MF src\lib\OpenEXR\CMakeFiles\OpenEXR.dir\ImfBoxAttribute.cpp.obj.d -o src/lib/OpenEXR/CMakeFiles/OpenEXR.dir/ImfBoxAttribute.cpp.obj -c D:/_/B/src/openexr-3.3.5/src/lib/OpenEXR/ImfBoxAttribute.cpp
  In file included from D:/_/B/src/openexr-3.3.5/src/lib/OpenEXR/ImfBoxAttribute.cpp:24:
  In file included from D:/_/B/src/openexr-3.3.5/src/lib/OpenEXR/ImfBoxAttribute.h:20:
  In file included from D:/M/msys64/clang64/include/Imath/ImathBox.h:16:
  D:/M/msys64/clang64/include/Imath/ImathVec.h:1097:37: error: explicit specialization of 'length' after instantiation
   1097 | IMATH_HOSTDEVICE short Vec2<short>::length () const IMATH_NOEXCEPT = delete;
        |                                     ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:53:53: note: implicit instantiation first required here
     53 | template <class T> class IMATH_EXPORT_TEMPLATE_TYPE Vec2
        |                                                     ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:1100:37: error: explicit specialization of 'normalize' after instantiation
   1100 |                        Vec2<short>::normalize () IMATH_NOEXCEPT = delete;
        |                                     ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:53:53: note: implicit instantiation first required here
     53 | template <class T> class IMATH_EXPORT_TEMPLATE_TYPE Vec2
        |                                                     ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:1101:45: error: explicit specialization of 'normalizeExc' after instantiation
   1101 | template <> const Vec2<short>& Vec2<short>::normalizeExc ()     = delete;
        |                                             ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:53:53: note: implicit instantiation first required here
     53 | template <class T> class IMATH_EXPORT_TEMPLATE_TYPE Vec2
        |                                                     ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:1104:37: error: explicit specialization of 'normalizeNonNull' after instantiation
   1104 |                        Vec2<short>::normalizeNonNull () IMATH_NOEXCEPT = delete;
        |                                     ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:53:53: note: implicit instantiation first required here
     53 | template <class T> class IMATH_EXPORT_TEMPLATE_TYPE Vec2
        |                                                     ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:1107:31: error: explicit specialization of 'normalized' after instantiation
   1107 |                  Vec2<short>::normalized () const IMATH_NOEXCEPT = delete;
        |                               ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:53:53: note: implicit instantiation first required here
     53 | template <class T> class IMATH_EXPORT_TEMPLATE_TYPE Vec2
        |                                                     ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:1108:38: error: explicit specialization of 'normalizedExc' after instantiation
   1108 | template <> Vec2<short> Vec2<short>::normalizedExc () const      = delete;
        |                                      ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:53:53: note: implicit instantiation first required here
     53 | template <class T> class IMATH_EXPORT_TEMPLATE_TYPE Vec2
        |                                                     ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:1111:14: error: explicit specialization of 'normalizedNonNull' after instantiation
   1111 | Vec2<short>::normalizedNonNull () const IMATH_NOEXCEPT = delete;
        |              ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:53:53: note: implicit instantiation first required here
     53 | template <class T> class IMATH_EXPORT_TEMPLATE_TYPE Vec2
        |                                                     ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:1115:33: error: explicit specialization of 'length' after instantiation
   1115 | IMATH_HOSTDEVICE int Vec2<int>::length () const IMATH_NOEXCEPT = delete;
        |                                 ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:53:53: note: implicit instantiation first required here
     53 | template <class T> class IMATH_EXPORT_TEMPLATE_TYPE Vec2
        |                                                     ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:1118:41: error: explicit specialization of 'normalize' after instantiation
   1118 |                              Vec2<int>::normalize () IMATH_NOEXCEPT = delete;
        |                                         ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:53:53: note: implicit instantiation first required here
     53 | template <class T> class IMATH_EXPORT_TEMPLATE_TYPE Vec2
        |                                                     ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:1119:41: error: explicit specialization of 'normalizeExc' after instantiation
   1119 | template <> const Vec2<int>& Vec2<int>::normalizeExc ()             = delete;
        |                                         ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:53:53: note: implicit instantiation first required here
     53 | template <class T> class IMATH_EXPORT_TEMPLATE_TYPE Vec2
        |                                                     ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:1122:35: error: explicit specialization of 'normalizeNonNull' after instantiation
   1122 |                        Vec2<int>::normalizeNonNull () IMATH_NOEXCEPT = delete;
        |                                   ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:53:53: note: implicit instantiation first required here
     53 | template <class T> class IMATH_EXPORT_TEMPLATE_TYPE Vec2
        |                                                     ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:1125:34: error: explicit specialization of 'normalized' after instantiation
   1125 |                       Vec2<int>::normalized () const IMATH_NOEXCEPT = delete;
        |                                  ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:53:53: note: implicit instantiation first required here
     53 | template <class T> class IMATH_EXPORT_TEMPLATE_TYPE Vec2
        |                                                     ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:1126:34: error: explicit specialization of 'normalizedExc' after instantiation
   1126 | template <> Vec2<int> Vec2<int>::normalizedExc () const             = delete;
        |                                  ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:53:53: note: implicit instantiation first required here
     53 | template <class T> class IMATH_EXPORT_TEMPLATE_TYPE Vec2
        |                                                     ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:1129:29: error: explicit specialization of 'normalizedNonNull' after instantiation
   1129 |                  Vec2<int>::normalizedNonNull () const IMATH_NOEXCEPT = delete;
        |                             ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:53:53: note: implicit instantiation first required here
     53 | template <class T> class IMATH_EXPORT_TEMPLATE_TYPE Vec2
        |                                                     ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:1133:41: error: explicit specialization of 'length' after instantiation
   1133 | IMATH_HOSTDEVICE int64_t Vec2<int64_t>::length () const IMATH_NOEXCEPT = delete;
        |                                         ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:53:53: note: implicit instantiation first required here
     53 | template <class T> class IMATH_EXPORT_TEMPLATE_TYPE Vec2
        |                                                     ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:1136:39: error: explicit specialization of 'normalize' after instantiation
   1136 |                        Vec2<int64_t>::normalize () IMATH_NOEXCEPT = delete;
        |                                       ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:53:53: note: implicit instantiation first required here
     53 | template <class T> class IMATH_EXPORT_TEMPLATE_TYPE Vec2
        |                                                     ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:1137:49: error: explicit specialization of 'normalizeExc' after instantiation
   1137 | template <> const Vec2<int64_t>& Vec2<int64_t>::normalizeExc ()   = delete;
        |                                                 ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:53:53: note: implicit instantiation first required here
     53 | template <class T> class IMATH_EXPORT_TEMPLATE_TYPE Vec2
        |                                                     ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:1140:16: error: explicit specialization of 'normalizeNonNull' after instantiation
   1140 | Vec2<int64_t>::normalizeNonNull () IMATH_NOEXCEPT = delete;
        |                ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:53:53: note: implicit instantiation first required here
     53 | template <class T> class IMATH_EXPORT_TEMPLATE_TYPE Vec2
        |                                                     ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:1143:33: error: explicit specialization of 'normalized' after instantiation
   1143 |                  Vec2<int64_t>::normalized () const IMATH_NOEXCEPT = delete;
        |                                 ^
  D:/M/msys64/clang64/include/Imath/ImathVec.h:53:53: note: implicit instantiation first required here
     53 | template <class T> class IMATH_EXPORT_TEMPLATE_TYPE Vec2
        |                                                     ^
  fatal error: too many errors emitted, stopping now [-ferror-limit=]
  20 errors generated.

[kmilos]

Note that the MSYS2 Imath package is currently (3.1.12) patched to remove these declarations: https://github.com/msys2/MINGW-packages/blob/b4b1fb6682cccd522e1ed64a265a4bc36b20f6e7/mingw-w64-imath/0002-fix-openexr-clang-build.patch

[cary-ilm]

I'm working on a solution to this, an alternative to the =delete in ImathVec.h, but it's not quite working yet.