WIP: REMOTE_MODULE_TEST BUG: Fix DCMTK external module compatibility (ijg include paths + MSVC __cplusplus)#6072
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The DCMTK ExternalProject include path loop iterates over all
_ITKDCMTK_LIB_NAMES and adds ${lib}/include to
ITKDCMTK_INCLUDE_DIRS. The internal JPEG codec libraries (ijg8,
ijg12, ijg16) have no public headers, so these paths don't exist.
When exported in INTERFACE_INCLUDE_DIRECTORIES, CMake 3.x+ raises
an error in external modules that link against ITK::ITKDCMTKModule:
Imported target "ITK::ITKDCMTKModule" includes non-existent path
".../ITKDCMTK_ExtProject/ijg12/include"
Skip libs matching "^ijg" in the include path loop. These are
internal JPEG codecs used only by dcmjpeg and never needed in
consumer include paths.
Fixes ITKIOTransformDCMTK#17 (Linux build failure).
MSVC does not set __cplusplus to the correct value by default — it always returns 199711L regardless of the actual standard being compiled with. DCMTK's osconfig.h checks: #if defined(HAVE_CXX11) && __cplusplus < 201103L #error DCMTK was configured to use C++11 features, but ... #endif This fires on MSVC even when C++17 is enabled because __cplusplus reports 199711L. The /Zc:__cplusplus flag (available since VS2017 15.7, MSVC 19.14) makes the compiler report the true value. ITK already requires MSVC 19.20+ so this flag is always available. Fixes ITKIOTransformDCMTK#17 (Windows build failure).
This was referenced Apr 15, 2026
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Fix two DCMTK issues that break external module builds (e.g., ITKIOTransformDCMTK). Backport candidate for v5.4.6 per #6051.
Issue 1 (Linux): DCMTK internal JPEG codec libraries (ijg8, ijg12, ijg16) are included in the INTERFACE_INCLUDE_DIRECTORIES loop, but these libraries have no public headers. The exported paths don't exist, causing CMake configure errors in external modules.
Issue 2 (Windows): MSVC reports
__cplusplus == 199711Lregardless of the actual C++ standard. DCMTK'sosconfig.hchecks__cplusplus >= 201103Land raises#erroron MSVC even with C++17 enabled. Adding/Zc:__cplusplusmakes MSVC report the true value.Downstream impact
Commits
ijg8/ijg12/ijg16in the include path loopitkCompilerChecks.cmake, append/Zc:__cpluspluswhen building with MSVC (available since 19.14, we require 19.20+)