Statically Link 3rd Party Library Built with CMake into Qt 5.12.11 Project Built with QMake in Qt Creator

Crag_Hack

@SGaist I think I found the problem after some head smashing... in the CMakeLists.txt for the Simple Mail library it has:

add_library(SimpleMail2Qt${QT_VERSION_MAJOR} SHARED
    ${simplemailqt_SRC}
    ${simplemailqt_HEADERS}
    ${simplemailqt_HEADERS_PRIVATE}
)

The ${simplemailqt_***} variables are just lists of source files.

I changed to STATIC instead of shared but then get a bunch of inconsistent dll linkage warnings and three definition of dllimport static data member not allowed errors (see screenshot below).

Does that mean the developer designed the library to be shared only? Would it take a herculean effort to convert it to static? Thanks again!

Crag_Hack

@SGaist Got any input? A little might go a long way, thanks!

SGaist

Sorry I lost track of this thread. Can you post the exact link of the sources of that library (just to be sure we are looking at the same thing).

Crag_Hack

@SGaist
Here 'tis. I'm looking at the CMakeLists.txt in the src directory which is the location of the library code.

SGaist

I found the issue, there's a glitch in the src CMakeLists.txt, they have hard coded the library build as shared. Just removed that from the add_library line, configure the build to be static and you will have a static build of it.

Crag_Hack

@SGaist Thanks, SGaist, I found the same issue, see three posts ago. I just now tried leaving both STATIC and SHARED out of add_library and get the same compile errors/warnings as using STATIC with add_library.

I have the same question as before... Does this mean the developer designed the library to be shared only? Would it take a herculean effort to convert it to static? Thanks again!

SGaist

Do you mean you can't get a static build of the library ?

Crag_Hack

@SGaist These are the errors/warnings I get when I try to build the library without the SHARED option passed to add_library:

alt text

SGaist

With BUILD_SHARED_LIBS set to OFF ?

Crag_Hack

@SGaist Yep that's correct.

Crag_Hack

I tried add_compile_definitions(PLUGIN_LIBRARY) to both CMakeLists.txt with no luck.

Crag_Hack

@SGaist I might have just gotten it to work... will confirm tomorrow but it looks pretty convincing. I added add_compile_definitions(SimpleMail2Qt5_EXPORTS) to both CMakeLists.txt's. Forgot how I arrived at this necessity I'll try to remember tomorrrow :) Thanks for the help!

Crag_Hack

@SGaist I finally got the library to compile statically. I had to remove SHARED from add_library, set BUILD_SHARED_LIBS to off, and add add_compile_definitions(SimpleMail2Qt5_EXPORTS) to CMakeLists.txt.

In the SimpleMail project we have src/smtpexports.h with:

#if defined(SimpleMail2Qt5_EXPORTS) || defined(SimpleMail2Qt6_EXPORTS)
#define SMTP_EXPORT Q_DECL_EXPORT
#else
#define SMTP_EXPORT Q_DECL_IMPORT
#endif

The Q_DECL_EXPORT seems to be essential.

Now I get another error! Bloody hell.

Running NMake trying to build my project that uses SimpleMail I get some of these:

SimpleMail2Qt5.lib(emailaddress.cpp.obj) : error LNK2038: mismatch detected for 'RuntimeLibrary': value 'MD_DynamicRelease' doesn't match value 'MT_StaticRelease' in qtsingleapplication.obj

and a lot of these:

SimpleMail2Qt5.lib(mimemessage.cpp.obj) : error LNK2019: unresolved external symbol "__declspec(dllimport) public: __cdecl QByteArray::QByteArray(class QByteArray const &)" (__imp_??0QByteArray@@QEAA@AEBV0@@Z) referenced in function "public: __cdecl QStringBuilder<class QByteArray,class QByteArray>::operator class QByteArray(void)const " (??B?$QStringBuilder@VQByteArray@@V1@@@QEBA?AVQByteArray@@XZ)

and these:

SimpleMail2Qt5.lib(mimepart.cpp.obj) : error LNK2001: unresolved external symbol "__declspec(dllimport) public: __cdecl QByteArray::QByteArray(class QByteArray const &)" (__imp_??0QByteArray@@QEAA@AEBV0@@Z)

I'll google these guys... do you know off the top of your head what's going on?
Thanks

Crag_Hack

@SGaist ( or anybody ) Making progress on this, it looks like error LNK2038: mismatch detected for 'RuntimeLibrary': value 'MD_DynamicRelease' doesn't match value 'MT_StaticRelease' is due to symbol mismatch detected by the linker. So one part of the program uses the DLL version of the run time library and another uses static version of the run time library. See here and here.

For those who aren't following this thread I am getting this error (and many others probably related to this) when trying to compile my project using a static build of the SimpleMail plugin:

SimpleMail2Qt5.lib(emailaddress.cpp.obj) : error LNK2038: mismatch detected for 'RuntimeLibrary': value 'MD_DynamicRelease' doesn't match value 'MT_StaticRelease' in qtsingleapplication.obj

The fix should be easy, just make the library use the static run time library. I tried to do this in CMakeLists.txt using both:

set_property(TARGET SimpleMail2Qt${QT_VERSION_MAJOR} PROPERTY MSVC_RUNTIME_LIBRARY "MultiThreaded$<$<CONFIG:Debug>:Debug>")
//used at the end of the CMakeLists.txt in src directory of SimpleMail project directory

and

set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreaded$<$<CONFIG:Debug>:Debug>")
//used at the beginning of both CMakeLists.txt files (the one in the SimpleMail root and src subdirectory of SimpleMail project)

but still get the linker error. See here and here and for these CMake variables. Any idea what might be wrong? Is there another way to specify whether to use the static or dll run time library when building a project using CMake and Qt Creator?

Crag_Hack

@SGaist Hi SGaist, any idea what's causing the LNK2038 error previously mentioned? Is it not using the static run-time library for building the SimpleMail library? Shouldn't CMake set variable commands shown remedy the situation? Thanks!

SGaist

Might be a silly question but are you sure you are using the same version of Qt to build the library and your project ?

Crag_Hack

@SGaist Yes they are both 5.12.11.

SGaist · @SGaist Yes they are both 5.12.11.

And that is a dynamic build of Qt ?

Crag_Hack

@SGaist The program is built statically but the library is built using Qt Creator so dynamic right? I tried building the library static as well but bot a bunch of errors, could try again...

SGaist

No need to build Qt statically, I am just trying to asses the situation as I currently can't figure out why the two run times are being used. The fact that the library is static does not mean that it shall use the static runtime. All the more when using a shared build of Qt.