QGIS: Error LNK2019 using QApplication - c++

Question

I'm trying to create a project using the QGIS class "QApplication" but it seems to fail due to an error I can´t understand.
I'm using this build version of QGIS made for QT5.7, VS2015, W10 x64 and my main.cpp just containts the following lines:
#define CORE_EXPORT __declspec(dllexport)
#include "QGisTest.h"
#include <QtWidgets/QApplication>
#include <qgsapplication.h>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QGisTest w;
w.show();
return a.exec();
}
And when I try to build it, these errors show up:
1>------ Build started: Project: QGisTest, Configuration: Release x64 ------
1> moc_qgsapplication.cpp
1> Creating library C:\Users\GRODRIGUEZ\Documents\Visual Studio 2015\Projects\QGisTest\x64\Release\QGisTest.lib and object C:\Users\GRODRIGUEZ\Documents\Visual Studio 2015\Projects\QGisTest\x64\Release\QGisTest.exp
1>moc_qgsapplication.obj : error LNK2019: unresolved external symbol "private: static class QMap<class QString,class QString> QgsApplication::mSystemEnvVars21800" (?mSystemEnvVars21800#QgsApplication##0V?$QMap#VQString##V1###A) referenced in function "public: static class QMap<class QString,class QString> __cdecl QgsApplication::systemEnvVars(void)" (?systemEnvVars#QgsApplication##SA?AV?$QMap#VQString##V1###XZ)
1>main.obj : error LNK2001: unresolved external symbol "private: static class QMap<class QString,class QString> QgsApplication::mSystemEnvVars21800" (?mSystemEnvVars21800#QgsApplication##0V?$QMap#VQString##V1###A)
1>moc_qgsapplication.obj : error LNK2019: unresolved external symbol "private: static bool QgsApplication::mRunningFromBuildDir21800" (?mRunningFromBuildDir21800#QgsApplication##0_NA) referenced in function "public: static bool __cdecl QgsApplication::isRunningFromBuildDir(void)" (?isRunningFromBuildDir#QgsApplication##SA_NXZ)
1>main.obj : error LNK2001: unresolved external symbol "private: static bool QgsApplication::mRunningFromBuildDir21800" (?mRunningFromBuildDir21800#QgsApplication##0_NA)
1>moc_qgsapplication.obj : error LNK2019: unresolved external symbol "private: static class QString QgsApplication::mBuildSourcePath21800" (?mBuildSourcePath21800#QgsApplication##0VQString##A) referenced in function "public: static class QString __cdecl QgsApplication::buildSourcePath(void)" (?buildSourcePath#QgsApplication##SA?AVQString##XZ)
1>main.obj : error LNK2001: unresolved external symbol "private: static class QString QgsApplication::mBuildSourcePath21800" (?mBuildSourcePath21800#QgsApplication##0VQString##A)
1>moc_qgsapplication.obj : error LNK2019: unresolved external symbol "private: static class QString QgsApplication::mCfgIntDir21800" (?mCfgIntDir21800#QgsApplication##0VQString##A) referenced in function "public: static class QString __cdecl QgsApplication::cfgIntDir(void)" (?cfgIntDir#QgsApplication##SA?AVQString##XZ)
1>main.obj : error LNK2001: unresolved external symbol "private: static class QString QgsApplication::mCfgIntDir21800" (?mCfgIntDir21800#QgsApplication##0VQString##A)
1>moc_qgsapplication.obj : error LNK2019: unresolved external symbol "private: static class QString QgsApplication::mBuildOutputPath21800" (?mBuildOutputPath21800#QgsApplication##0VQString##A) referenced in function "public: static class QString __cdecl QgsApplication::buildOutputPath(void)" (?buildOutputPath#QgsApplication##SA?AVQString##XZ)
1>main.obj : error LNK2001: unresolved external symbol "private: static class QString QgsApplication::mBuildOutputPath21800" (?mBuildOutputPath21800#QgsApplication##0VQString##A)
1>moc_qgsapplication.obj : error LNK2019: unresolved external symbol "private: static class QStringList QgsApplication::mGdalSkipList21800" (?mGdalSkipList21800#QgsApplication##0VQStringList##A) referenced in function "public: static class QStringList __cdecl QgsApplication::skippedGdalDrivers(void)" (?skippedGdalDrivers#QgsApplication##SA?AVQStringList##XZ)
1>main.obj : error LNK2001: unresolved external symbol "private: static class QStringList QgsApplication::mGdalSkipList21800" (?mGdalSkipList21800#QgsApplication##0VQStringList##A)
1>moc_qgsapplication.obj : error LNK2019: unresolved external symbol "private: static int QgsApplication::mMaxThreads21800" (?mMaxThreads21800#QgsApplication##0HA) referenced in function "public: static int __cdecl QgsApplication::maxThreads(void)" (?maxThreads#QgsApplication##SAHXZ)
1>main.obj : error LNK2001: unresolved external symbol "private: static int QgsApplication::mMaxThreads21800" (?mMaxThreads21800#QgsApplication##0HA)
1>C:\Users\GRODRIGUEZ\Documents\Visual Studio 2015\Projects\QGisTest\x64\Release\\QGisTest.exe : fatal error LNK1120: 7 unresolved externals
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
I also added to the project this "moc_qgsapplication.cpp" and wrote the line:
#define CORE_EXPORT __declspec(dllexport)
to avoid other compilation problems and linked to the project the QGIS and QT 5.7 libs.
Any idea how to fix it?
EDIT:
I have changed the two lines of main.cpp as suggested and now contains the following code:
#define CORE_EXPORT __declspec(dllimport)
#include "QGisTest.h"
#include <QApplication>
#include <qgsapplication.h>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QGisTest w;
w.show();
return a.exec();
}
but when I try to build it, these erros still show up:
1>------ Build started: Project: QGisTest, Configuration: Release x64 ------
1> moc_qgsapplication.cpp
1> main.cpp
1> Generating Code...
1> Creating library C:\Users\GRODRIGUEZ\Documents\Visual Studio 2015\Projects\QGisTest\x64\Release\QGisTest.lib and object C:\Users\GRODRIGUEZ\Documents\Visual Studio 2015\Projects\QGisTest\x64\Release\QGisTest.exp
1>moc_qgsapplication.obj : error LNK2019: unresolved external symbol "private: static class QMap<class QString,class QString> QgsApplication::mSystemEnvVars21800" (?mSystemEnvVars21800#QgsApplication##0V?$QMap#VQString##V1###A) referenced in function "public: static class QMap<class QString,class QString> __cdecl QgsApplication::systemEnvVars(void)" (?systemEnvVars#QgsApplication##SA?AV?$QMap#VQString##V1###XZ)
1>moc_qgsapplication.obj : error LNK2019: unresolved external symbol "private: static bool QgsApplication::mRunningFromBuildDir21800" (?mRunningFromBuildDir21800#QgsApplication##0_NA) referenced in function "public: static bool __cdecl QgsApplication::isRunningFromBuildDir(void)" (?isRunningFromBuildDir#QgsApplication##SA_NXZ)
1>moc_qgsapplication.obj : error LNK2019: unresolved external symbol "private: static class QString QgsApplication::mBuildSourcePath21800" (?mBuildSourcePath21800#QgsApplication##0VQString##A) referenced in function "public: static class QString __cdecl QgsApplication::buildSourcePath(void)" (?buildSourcePath#QgsApplication##SA?AVQString##XZ)
1>moc_qgsapplication.obj : error LNK2019: unresolved external symbol "private: static class QString QgsApplication::mCfgIntDir21800" (?mCfgIntDir21800#QgsApplication##0VQString##A) referenced in function "public: static class QString __cdecl QgsApplication::cfgIntDir(void)" (?cfgIntDir#QgsApplication##SA?AVQString##XZ)
1>moc_qgsapplication.obj : error LNK2019: unresolved external symbol "private: static class QString QgsApplication::mBuildOutputPath21800" (?mBuildOutputPath21800#QgsApplication##0VQString##A) referenced in function "public: static class QString __cdecl QgsApplication::buildOutputPath(void)" (?buildOutputPath#QgsApplication##SA?AVQString##XZ)
1>moc_qgsapplication.obj : error LNK2019: unresolved external symbol "private: static class QStringList QgsApplication::mGdalSkipList21800" (?mGdalSkipList21800#QgsApplication##0VQStringList##A) referenced in function "public: static class QStringList __cdecl QgsApplication::skippedGdalDrivers(void)" (?skippedGdalDrivers#QgsApplication##SA?AVQStringList##XZ)
1>moc_qgsapplication.obj : error LNK2019: unresolved external symbol "private: static int QgsApplication::mMaxThreads21800" (?mMaxThreads21800#QgsApplication##0HA) referenced in function "public: static int __cdecl QgsApplication::maxThreads(void)" (?maxThreads#QgsApplication##SAHXZ)
1>C:\Users\GRODRIGUEZ\Documents\Visual Studio 2015\Projects\QGisTest\x64\Release\\QGisTest.exe : fatal error LNK1120: 7 unresolved externals
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========