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qtcompiler-errorslinkerlnk2019lnk2001

Linker errors LNK2001 and LNK2019

I am compiling my Qt project using compiler MSVC2008, and I am getting linker errors like-

_class_name.obj_:error LNK2001: unresolved external symbol "public: static struct QMetaObject...."... referenced in a function "_function_name_"

_class_name.obj_:error LNK2019: unresolved external symbol "public: static struct QMetaObject..." ... referenced in a function "_function_name_"

I have few basic queries-

  1. what does it mean by errors LNK2001 and LNK2019?

  2. Why these error occurs?

  3. How to resolve these?

NOTE: I am using QtCreater so build system uses qmake and compiler used is MSVC2008.

Solution

    1. In a nutshell, you used a function which is declared but not defined.

    2. It should be caused by your classes using Qt functionality (like signal-slots) but incorrectly.

    3. Here's possibilities I can think of:

      3-a. Double check you've written "Q_OBJECT" at the beginning of your class that use Qt functionality.

      3-b. You call "moc" property, i.e. check if your Qt Visual Studio plugin is installed and enabled.