MFC Custom Control in a MFC DLL
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From: Luigino on 16 Oct 2009 08:19 > This is linker error message. The real reason for the error message is > that the linker does not see the implementation. Either you do not have > the implementation for the CCaChart:.CCaChart(void) constructor of you > are not including relevant object file on command line. HI ismo, as I said the VS DLL ClassWizard added the constructor and destructor which are: ..CPP CCaChart::CCaChart() { iGraphType = GRAPH_BARS; RegisterWindowClass(); } CCaChart::~CCaChart() { } ..H class CCaChart : public CWnd { DECLARE_DYNAMIC(CCaChart) public: CCaChart(); public: virtual ~CCaChart(); .. .. .. (plus other functions...) } and as I said before, I added in test application's properties the path and the name of the lib file... even I also added in the test application file the include to the header... So in fact it's weird to get this error... that's why I'm here asking you... Thanks Luigi
From: Joseph M. Newcomer on 16 Oct 2009 09:47 See below... On Fri, 16 Oct 2009 00:59:16 -0700 (PDT), Luigino <npuleio(a)rocketmail.com> wrote: >I tried this too: > >CStatic* c_CStaticPlaced = (CStatic *)GetDlgItem(IDC_MYSTATIC); **** It is completely silly to use GetDlgItem in this case; you should create a control variable! **** >CRect r; >c_CStaticPlaced->GetWindowRect(&r); >ScreenToClient(&r); >CCaChart* c_MyControl = new CCaChart(); **** Why do you new a 'new' here? This is silly. You can simply declare a CCaChart variable in your class definition! There is ABSOLUTELY no reason to do a 'new'. **** >CWnd* pWnd = c_CStaticPlaced->GetDlgItem(c_CStaticPlaced->GetDlgCtrlID >()); >c_MyControl->Create(r, pWnd); >c_CStaticPlaced->DestroyWindow(); > >but I get this error: > >1>test_chartDlg.obj : error LNK2019: unresolved external symbol >"public: __thiscall CCaChart::CCaChart(void)" (??0CCaChart@@QAE(a)XZ) >referenced in function "protected: virtual int __thiscall >Ctest_chartDlg::OnInitDialog(void)" (? >OnInitDialog(a)Ctest_chartDlg@@MAEHXZ) **** OnInitDialog is always virtual, so I see no issue here; I see no reference to CaChart as virtual; what you probably failed to do was include the .lib file for your DLL, which is a common mistake. **** > >but the constructor CaChart isn't declared as virtual in the header's >class, plus it's public... > >Any suggest?... >Thanks >Ciao >Luigi Joseph M. Newcomer [MVP] email: newcomer(a)flounder.com Web: http://www.flounder.com MVP Tips: http://www.flounder.com/mvp_tips.htm
From: Joseph M. Newcomer on 16 Oct 2009 09:49 So what? VS adding a declaration does not make that declaration visible to the client of the DLL if you fail to include the .lib file in the linker command line. You are confusing the C++ compiler with the linker here. They are different, and what you do in C++ has no implicit effect on the linker. Go to the Linker, Inputs, and add your .lib file to the additional libraries line. joe On Fri, 16 Oct 2009 05:19:05 -0700 (PDT), Luigino <npuleio(a)rocketmail.com> wrote: >> This is linker error message. The real reason for the error message is >> that the linker does not see the implementation. Either you do not have >> the implementation for the CCaChart:.CCaChart(void) constructor of you >> are not including relevant object file on command line. > >HI ismo, > >as I said the VS DLL ClassWizard added the constructor and destructor >which are: > >.CPP > >CCaChart::CCaChart() >{ > iGraphType = GRAPH_BARS; > RegisterWindowClass(); >} > >CCaChart::~CCaChart() >{ >} > >.H > >class CCaChart : public CWnd >{ > DECLARE_DYNAMIC(CCaChart) > >public: > CCaChart(); > >public: > virtual ~CCaChart(); >. >. >. >(plus other functions...) >} > >and as I said before, I added in test application's properties the >path and the name of the lib file... >even I also added in the test application file the include to the >header... >So in fact it's weird to get this error... that's why I'm here asking >you... > >Thanks >Luigi Joseph M. Newcomer [MVP] email: newcomer(a)flounder.com Web: http://www.flounder.com MVP Tips: http://www.flounder.com/mvp_tips.htm
From: Luigino on 16 Oct 2009 11:42 > confusing the C++ compiler with the linker here. They are different, and what you do in > C++ has no implicit effect on the linker. Go to the Linker, Inputs, and add your .lib > file to the additional libraries line. Ehm I did... I put under Linker-General in Additional Library Directories the path of that Debug directory where the .lib file is created once compiled the DLL and I added under Linker-Input, in Additional Dependencies that CACharts.lib..... So I also created now a control variable (from the class add variable wizard) for this and implemented the code: CRect rect; c_MyStaticControl.GetWindowRect(&rect); ScreenToClient(&rect); CCaChart c_MyControl; c_MyControl.Create(rect, GetDlgItem (c_MyStaticControl.GetDlgCtrlID())); c_MyStaticControl.DestroyWindow(); but I get these linker errors: 1>test_chartDlg.obj : error LNK2019: unresolved external symbol "public: virtual __thiscall CCaChart::~CCaChart(void)" (?? 1CCaChart@@UAE(a)XZ) referenced in function "protected: virtual int __thiscall Ctest_chartDlg::OnInitDialog(void)" (? OnInitDialog(a)Ctest_chartDlg@@MAEHXZ) 1>test_chartDlg.obj : error LNK2019: unresolved external symbol "public: virtual int __thiscall CCaChart::Create(class CRect const &,class CWnd *)" (?Create(a)CCaChart@@UAEHABVCRect@@PAVCWnd@@@Z) referenced in function "protected: virtual int __thiscall Ctest_chartDlg::OnInitDialog(void)" (? OnInitDialog(a)Ctest_chartDlg@@MAEHXZ) 1>test_chartDlg.obj : error LNK2019: unresolved external symbol "public: __thiscall CCaChart::CCaChart(void)" (??0CCaChart@@QAE(a)XZ) referenced in function "protected: virtual int __thiscall Ctest_chartDlg::OnInitDialog(void)" (? OnInitDialog(a)Ctest_chartDlg@@MAEHXZ) So, suspecting a possible issue of my VS2008, I tried to create from scratch with class wizards a simple stupid DLL without adding or modifying anything and trying to create a Test file from Visual Studio IDE itself and when it asks me to choose the DLL project to test, it returns "Unknown address 0"... then I try to create a test project for the example, adding the .lib and I get same linker error I pasted before...
From: Stephen Myers on 16 Oct 2009 13:15
Luigino wrote: >> confusing the C++ compiler with the linker here. They are different, and what you do in >> C++ has no implicit effect on the linker. Go to the Linker, Inputs, and add your .lib >> file to the additional libraries line. > > Ehm I did... I put under Linker-General in Additional Library > Directories the path of that Debug directory where the .lib file is > created once compiled the DLL and I added under Linker-Input, in > Additional Dependencies that CACharts.lib..... > So I also created now a control variable (from the class add variable > wizard) for this and implemented the code: > > CRect rect; > c_MyStaticControl.GetWindowRect(&rect); > ScreenToClient(&rect); > CCaChart c_MyControl; > c_MyControl.Create(rect, GetDlgItem > (c_MyStaticControl.GetDlgCtrlID())); > c_MyStaticControl.DestroyWindow(); > > but I get these linker errors: > > 1>test_chartDlg.obj : error LNK2019: unresolved external symbol > "public: virtual __thiscall CCaChart::~CCaChart(void)" (?? > 1CCaChart@@UAE(a)XZ) referenced in function "protected: virtual int > __thiscall Ctest_chartDlg::OnInitDialog(void)" (? > OnInitDialog(a)Ctest_chartDlg@@MAEHXZ) > 1>test_chartDlg.obj : error LNK2019: unresolved external symbol > "public: virtual int __thiscall CCaChart::Create(class CRect const > &,class CWnd *)" (?Create(a)CCaChart@@UAEHABVCRect@@PAVCWnd@@@Z) > referenced in function "protected: virtual int __thiscall > Ctest_chartDlg::OnInitDialog(void)" (? > OnInitDialog(a)Ctest_chartDlg@@MAEHXZ) > 1>test_chartDlg.obj : error LNK2019: unresolved external symbol > "public: __thiscall CCaChart::CCaChart(void)" (??0CCaChart@@QAE(a)XZ) > referenced in function "protected: virtual int __thiscall > Ctest_chartDlg::OnInitDialog(void)" (? > OnInitDialog(a)Ctest_chartDlg@@MAEHXZ) > > So, suspecting a possible issue of my VS2008, I tried to create from > scratch with class wizards a simple stupid DLL without adding or > modifying anything and trying to create a Test file from Visual Studio > IDE itself and when it asks me to choose the DLL project to test, it > returns "Unknown address 0"... then I try to create a test project for > the example, adding the .lib and I get same linker error I pasted > before... I thought you needed to export the symbols in the library. In CaChart.h Something like #ifdef MYLIB_BUILD #define MYDLL_IO _declspec(dllexport) //conditional on MYLIB_BUILD #else #define MYDLL_IO _declspec(dllimport) #endif class MYDLL_IO CCaChart: public ... Then add MYLIB_BUILD to the library project Configuration Properties C/C++ Preprocessor Preprocessor Defines Steve |