Unresolved External Symbol "Public: Virtual Struct Qmetaobject Const * _Thiscall Parent

Unresolved external symbol public: virtual struct QMetaObject const * __thiscall Parent

You should delete the debug folder of your application and run it again to correct this problem.

cmake qt6: unresolved external symbol “public: virtual struct QMetaObject”

As @Tsyvarev has pointed out, your handling of the GLOBAL_EXPORTS definition is wrong.

You should export the symbols if the GLOBAL_EXPORTS definition is set, therefore it should read (note: I changed #ifndef to #ifdef):

#ifdef GLOBAL_EXPORTS
    #define GLOBAL_EXPORT __declspec(dllexport)
#else
    #define GLOBAL_EXPORT __declspec(dllimport)
#endif // !GLOBAL_EXPORTS

Then in your CMakeLists.txt of the export_dll project you should add a line defining GLOBAL_EXPORTS:

set(CMAKE_AUTOMOC 1)
add_library(export_dll SHARED ${SOURCES} ${HEADERS})
set_target_properties(export_dll PROPERTIES COMPILE_DEFINITIONS GLOBAL_EXPORTS)
find_package(Qt6 REQUIRED COMPONENTS Widgets Core Gui)
target_link_libraries(export_dll PRIVATE Qt6::Widgets Qt6::Core Qt6::Gui)

By doing this __declspec(dllexport) will be added to the symbols when creating the DLL and every consumer of the DLL will automatically get the symbols with a proper __declspec(dllimport) set.

Unresolved external symbol struct MonthlyBudget_cdecl actual(void)

Removed () from actual() and all mentions. Fixed the program.

QAbstractItemModel for QMetaObject, do I have to write it myself?

If you are representing a tree of QObjects then QStandardItemModel will probably suit your needs. If not, you would probably subclass that instead of QAbstractItemModel.

log4cplus unresolved external symbol LNK2001

A Windows UNICODE build is built with TCHAR etc. being defined as wchar_t etc. When not building with UNICODE defined as build with TCHAR defined as char etc.

Building one library with UNICODE defined and attempting to link it in a project where UNICODE is not defined will result in linker errors since there will be a mismatch in the definition of TCHAR; char vs. wchar_t.

To correct this, build all the required libraries and projects with a consistent definition of UNICODE (and _UNICODE).

This can be done with either;

#define UNICODE
#define _UNICODE

Or in the project settings;

Project Properties > General > Project Defaults > Character Set

Or on the command line;

/DUNICODE /D_UNICODE

The alternative is applicable as well, if UNICODE is not intended to be used, make sure the defines are not set, and/or the multi-character setting is used in the projects and consistently applied.

Do not forget to be consistent between the "Release" and "Debug" builds as well.

C++ override virtual method throws an error LNK2001: unresolved external symbol

First of all, you are misusing the term "children". What you mean by that is subclasses. Children means something different in the Qt world.

The probable reason is that you do not have the corresponding source files in your SOURCES variable in your qmake project file.

Once you make that modiication, make sure qmake is rerun properly.

---

Related Topics