Building qt from source (debug) error LNK2038

[Norzka]

Hey,

So I am trying to build qt from source in debug. Whenever I try to build release, everything is fine but whenever I build in debug, I get 2 errors which repeat for many files and 1 error at the very end. The 2 errors are:

error LNK2038: mismatch detected for '_ITERATOR_DEBUG_LEVEL': value '0' doesn't match value '2'
error LNK2038: mismatch detected for 'RuntimeLibrary': value 'MD_DynamicRelease' doesn't match value 'MDd_DynamicDebug'

and the single end error is:

LINK : warning LNK4098: defaultlib 'MSVCRT' conflicts with use of other libs; use /NODEFAULTLIB:library

and this happens with every single variant of the configure/build command I could think of. here are 2 version:

cd <QTsrc>
mkdir build && cd build
..\configure.bat -debug -prefix "D:\Libraries\Qt\6.6.0\BuildDebug" -skip webengine -nomake tests -nomake examples -- -DCMAKE_BUILD_TYPE=Debug -DCMAKE_CXX_FLAGS_DEBUG="/Zi /Ob0 /Od /RTC1 /MDd"&& cmake --build . --parallel && cmake --install .

and

cd <QTsrc>
mkdir build && cd build
cmake .. -G Ninja -DCMAKE_PREFIX_PATH="D:\Libraries\Qt\6.6.0\BuildDebug" -DCMAKE_BUILD_TYPE=Debug -DCMAKE_CXX_FLAGS_DEBUG="/Zi /Ob0 /Od /RTC1 /MDd" -DCMAKE_C_FLAGS_DEBUG="/Zi /Ob0 /Od /RTC1 /MDd" -DWEBENGINE_SKIP=ON -DBUILD_TESTS=OFF -DBUILD_EXAMPLES=OFF && cmake --build . --parallel && cmake --install .

Many thanks in advance.

[Christian Ehrlicher]

Don't set the CMAKE_BUILD_TYPE and all the cxx flags - you most likely mix some stuff up. Let confnfigure.bar build all the stuff for you without those settings. Then you will get the correct Qt debug and release dlls.

[Norzka]

@Christian-Ehrlicher well thats what I was trying before, just using the -debug flag without the cmake flags. and that would result in the same error

[Christian Ehrlicher]

@Norzka said in Building qt from source (debug) error LNK2038:

@Christian-Ehrlicher well thats what I was trying before, just using the -debug flag without the cmake flags. and that would result in the same error

Don't set debug at all. Configure will do the right thing.

[Norzka]

@Christian-Ehrlicher well I want debug so I can easier debug my program, and whenever I run the configure command without the debug flag, it defaults to -debug-and-release which causes the same error

[Christian Ehrlicher]

Delete your build directory and start over. Don't specify any compiler flags - its' not needed.
Also why don't you use pre-compiled Qt libs?

[Norzka]

@Christian-Ehrlicher I have tried that too. I get the same error. And I could, but I get a runtime error, something about string conversion, looking online suggests that it is to do with QT and your project being compiled with different STLs, so that's what made me try to build from source. The thing is since I can build release, I can work on projects using QT, but if I run into some problem, I have to debug without using the Visual Studio debugger.

[Christian Ehrlicher]

@Norzka said in Building qt from source (debug) error LNK2038:

I have tried that too. I get the same error. And I could, but I get a runtime error, something about string conversion, looking online suggests that it is to do with QT and your project being compiled with different STLs, so that's what made me try to build from source.

From what are you talking? Using your Qt or the pre-compiled ones?

Use the pre-compiled ones with a proper CMakeLists.txt for your project and you won't get problems with different runtimes. Somehwere you mix /MT(d) with /MD(d) which must not be done.