`-C config/cacheinit.cmake` is required for configuration in hdf5 2.0 / missing `DEBUG_POSTFIX`

[Andrej730]

Hi! On Windows for hdf5 <2.0 when configuring with cmake .. -G Ninja -DCMAKE_INSTALL_PREFIX="installation" -DCMAKE_BUILD_TYPE=Debug it resulted in libraries having debug posfix - e.g. hdf5_D.lib, instead of hdf5.lib.

But in hdf5 2.0 it's no longer the case and hdf5.lib is also produced for Debug build.
Reading through the cmake files, it seems it's started from #5600 - when CMAKE_DEBUG_POSTFIX was moved to cacheinit.cmake.

Does it mean that standard way of configuration is now always requires cmake .. -C cacheinit.cmake? It would be kind of awkward, since typically you expect from repo to configure with just cmake .., unless you're using some kind of preset.

If it is required, then it seems cacheinit.cmake is missing in the examples below from the installation instructions:

hdf5/release_docs/INSTALL_CMake.txt

Lines 326 to 335 in 2cee17d

	On Windows 32 bit
	cmake -G "Visual Studio 16 2019" -A Win32 -DCMAKE_BUILD_TYPE:STRING=Release -DBUILD_SHARED_LIBS:BOOL=OFF -DBUILD_TESTING:BOOL=ON -DHDF5_BUILD_TOOLS:BOOL=ON ..\hdf5-2."X"."Y"
	On Windows 64 bit
	cmake -G "Visual Studio 16 2019" -A x64 -DCMAKE_BUILD_TYPE:STRING=Release -DBUILD_SHARED_LIBS:BOOL=OFF -DBUILD_TESTING:BOOL=ON -DHDF5_BUILD_TOOLS:BOOL=ON ..\hdf5-2."X"."Y"
	On Linux and Mac
	cmake -G "Unix Makefiles" -DCMAKE_BUILD_TYPE:STRING=Release -DBUILD_SHARED_LIBS:BOOL=OFF -DBUILD_TESTING:BOOL=ON -DHDF5_BUILD_TOOLS:BOOL=ON ../hdf5-2."X"."Y"
	where "X" is the current release version.

But even providing it and building with cmake .. -C ../config/cmake/cacheinit.cmake -G Ninja -DCMAKE_INSTALL_PREFIX="L:\oblivion\hdf5-install\" -DCMAKE_BUILD_TYPE=Debug -DDBUILD_TESTING=OFF -DHDF5_ENABLE_Z_LIB_SUPPORT=OFF -DHDF5_BUILD_FORTRAN=OFF -DHDF5_BUILD_JAVA=OFF -DCMAKE_C_COMPILER_LAUNCHER=ccache -DCMAKE_CXX_COMPILER_LAUNCHER=ccache -DCMAKE_MSVC_DEBUG_INFORMATION_FORMAT=Embedded -DCMAKE_POLICY_CMP0141=NEW -DHDF5_BUILD_TOOLS=OFF -DHDF5_BUILD_EXAMPLES=OFF -DHDF5_BUILD_UTILS=OFF results in hdf5.lib, not hdf5_d.lib.

[Andrej730]

Investigating some more, it seems ../config/cmake/cacheinit.cmake is executed in a separate context in it's own variables namespace (unlike include(config/cmake/cacheinit.cmake)), so it's local variables are not propagated to CMakeLists.txt. So I guess this can be resolved by setting CMAKE_DEBUG_POSTFIX in cache, not just as a local variable.

[Andrej730]

Another note - I believe #4647 wasn't resolved after all.

Since code is using if(NOT CMAKE_DEBUG_POSTFIX) to decide whether to add debug postifx, then providing -DCMAKE_DEBUG_POSTFIX="" would elaluate condition to TRUE and it will pass. So with -D it's possible only to override one postfix with another, not to remove it completely.

To correct this, condition should be if(NOT DEFINED CMAKE_DEBUG_POSTFIX).

[mattjala]

The cacheinit.cmake file should not be required for configuration in 2.0. The new default behavior is to always build without the debug postfix, to avoid the need to change the build/link process when changing the configuration type.

You're correct that the check will currently still set the values even if an empty string is manually provided - that should probably be updated to use a DEFINED check as you said.

As far as the scope of variables from cacheinit is concerned, I'm fairly sure that as long as cacheinit is used at build time via -C, that the value it sets for POSTFIX will be used for generation of the library files.

[Andrej730]

The cacheinit.cmake file should not be required for configuration in 2.0. The new default behavior is to always build without the debug postfix, to avoid the need to change the build/link process when changing the configuration type.

Okay. That's a bit unforunate then - it makes sense for Unix, where Release and Debug binaries are compatible, but on Windows they're not and not using debug postfix for them is a common source of confusion, leading to linking errors (e.g. Release libhdf5_cpp.lib has /FAILIFMISMATCH:_ITERATOR_DEBUG_LEVEL=0 that will prevent in from being linked to Debug build and vice versa).

With debug postfix it's possible to install both Release and Debug builds to the same folder and let cmake figure out which ones to use - since it will have both hdf5-targets-release.cmake and hdf5-targets-debug.cmake configs with separated paths to libraries, you don't really need to change build/link process and provide debug postfix yourself.

As far as the scope of variables from cacheinit is concerned, I'm fairly sure that as long as cacheinit is used at build time via -C, that the value it sets for POSTFIX will be used for generation of the library files.

No, the postfix won't be set, you can try it with the command below.
It seems cmake is using a separate scope for -C script and local variables are not propagated to the main cmake script.

cmake -S . -B build_ -C config/cmake/cacheinit.cmake -G Ninja -DCMAKE_INSTALL_PREFIX="build_/install" -DCMAKE_BUILD_TYPE=Debug -DDBUILD_TESTING=OFF -DHDF5_ENABLE_Z_LIB_SUPPORT=OFF -DHDF5_BUILD_FORTRAN=OFF -DHDF5_BUILD_JAVA=OFF -DCMAKE_C_COMPILER_LAUNCHER=ccache -DCMAKE_CXX_COMPILER_LAUNCHER=ccache -DCMAKE_MSVC_DEBUG_INFORMATION_FORMAT=Embedded -DHDF5_BUILD_TOOLS=OFF -DHDF5_BUILD_EXAMPLES=OFF -DHDF5_BUILD_UTILS=OFF

cmake --build build_ --target install

Resulting installation (no debug postfix):

-- Installing: L:/hdf5/build_/install/bin/hdf5.pdb
-- Installing: L:/hdf5/build_/install/lib/libhdf5.lib
-- Installing: L:/hdf5/build_/install/lib/hdf5.lib
-- Installing: L:/hdf5/build_/install/bin/hdf5.dll
-- Installing: L:/hdf5/build_/install/lib/pkgconfig/hdf5.pc
-- Installing: L:/hdf5/build_/install/bin/hdf5_hl.pdb
-- Installing: L:/hdf5/build_/install/lib/libhdf5_hl.lib
-- Installing: L:/hdf5/build_/install/lib/hdf5_hl.lib
-- Installing: L:/hdf5/build_/install/bin/hdf5_hl.dll
-- Installing: L:/hdf5/build_/install/lib/pkgconfig/hdf5_hl.pc
-- Installing: L:/hdf5/build_/install/bin/hdf5_cpp.pdb
-- Installing: L:/hdf5/build_/install/lib/libhdf5_cpp.lib
-- Installing: L:/hdf5/build_/install/lib/hdf5_cpp.lib
-- Installing: L:/hdf5/build_/install/bin/hdf5_cpp.dll
-- Installing: L:/hdf5/build_/install/lib/pkgconfig/hdf5_cpp.pc
-- Installing: L:/hdf5/build_/install/bin/hdf5_hl_cpp.pdb
-- Installing: L:/hdf5/build_/install/lib/libhdf5_hl_cpp.lib
-- Installing: L:/hdf5/build_/install/lib/hdf5_hl_cpp.lib
-- Installing: L:/hdf5/build_/install/bin/hdf5_hl_cpp.dll
-- Installing: L:/hdf5/build_/install/lib/pkgconfig/hdf5_hl_cpp.pc
-- Installing: L:/hdf5/build_/install/cmake/hdf5-targets.cmake
-- Installing: L:/hdf5/build_/install/cmake/hdf5-targets-debug.cmake
-- Installing: L:/hdf5/build_/install/cmake/hdf5-config.cmake
-- Installing: L:/hdf5/build_/install/cmake/hdf5-config-version.cmake
-- Installing: L:/hdf5/build_/install/lib/libhdf5.settings
-- Installing: L:/hdf5/build_/install/./LICENSE
-- Installing: L:/hdf5/build_/install/./USING_HDF5_CMake.txt
-- Installing: L:/hdf5/build_/install/./CHANGELOG.md
-- Installing: L:/hdf5/build_/install/./USING_HDF5_VS.txt
-- Installing: L:/hdf5/build_/install/bin/msvcp140.dll
-- Installing: L:/hdf5/build_/install/bin/msvcp140_1.dll
-- Installing: L:/hdf5/build_/install/bin/msvcp140_2.dll
-- Installing: L:/hdf5/build_/install/bin/msvcp140_atomic_wait.dll
-- Installing: L:/hdf5/build_/install/bin/msvcp140_codecvt_ids.dll
-- Installing: L:/hdf5/build_/install/bin/vcruntime140_1.dll
-- Installing: L:/hdf5/build_/install/bin/vcruntime140.dll
-- Installing: L:/hdf5/build_/install/bin/concrt140.dll
-- Up-to-date: L:/hdf5/build_/install/bin

[mattjala]

You're right - the value set by cacheinit for the POSTFIX currently has no effect because they're not added to the cache. I've added a fix to #6094.