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Matt L
767ac04b21
* Build the examples as C++11 to match the HDF5 C++ library The standalone examples build forces CMAKE_CXX_STANDARD 98, but H5public.h includes <cinttypes>, which requires C++11. Any C++ translation unit that includes hdf5.h is therefore affected, not just users of the C++ API, and the HDF5 C++ library itself is built as C++11 (config/flags/HDFCompilerCXXFlags.cmake). The C++ examples do not compile as a result, against static or shared HDF5 alike. Only the standalone build is affected, which is why this is not visible in ordinary use. The C++98 setting lives in BASIC_SETTINGS, and HDF5Examples/CMakeLists.txt skips that whole block when EXAMPLES_EXTERNALLY_CONFIGURED is set -- which HDF5 does for its own in-tree example build (config/cmake/HDF5ExampleCache.cmake). Built in tree, the examples inherit HDF5's C++11 and compile normally, and that is the path the CI workflows exercise. The standalone path, where the C++98 setting does apply, is driven by the release scripts rather than by the workflows, and has the C++ examples off by default. * Select the examples' HL, Fortran and C++ libraries on the right variable When the examples are built standalone against an installed HDF5, the HL, Fortran and C++ branches choose between the shared and static libraries using BUILD_SHARED_LIBS, while the C branch just above them uses H5EXAMPLE_USE_SHARED_LIBS. H5EXAMPLE_USE_SHARED_LIBS is what decides whether the "shared" or the "static" component is requested from find_package, so only the matching HDF5_<linkage>_<lang>_FOUND variables are ever set. BUILD_SHARED_LIBS cannot select a linkage on its own; it can only agree or fail to match. Of its four combinations with H5EXAMPLE_USE_SHARED_LIBS, three produce no observable difference. In the fourth, H5EXAMPLE_USE_SHARED_LIBS=ON with BUILD_SHARED_LIBS unset, the shared branch is not taken and the static branch cannot be, so the HL, Fortran and C++ examples are disabled with "libs not found" even though the libraries are installed and were found. Use H5EXAMPLE_USE_SHARED_LIBS, which is the declared option and is already what the C branch uses. A build driven through config/examples/CTestScript.cmake does not reach the broken combination, because it configures with HDF5Examples/config/cmake/cacheinit.cmake, which forces BUILD_SHARED_LIBS=ON. A direct cmake invocation without that cache file does. In either case the HL, Fortran and C++ examples are off by default, so this is only visible once they are enabled. BUILD_SHARED_LIBS remains documented as a user option in config/examples/HDF5_Examples_options.cmake but no longer influences library selection; that comment should be revisited separately.