vtable

original link: QT Classic error message undefined reference to ' vtable for classnameThis error message is too common, the use of QT more than two months of friends can basically solve their own, because too classic, can give reference to the novice.The error message is generally similar to the following: undefined reference to ' vtable for classname Mywidget 'Occurs after the make command is executed.The r

object!So how does the compiler know where the correct code is located? In fact, the compiler does not know the correct position of the function body to be called during compilation, But it inserts a piece of code that can find the correct function body. This is calledLate binding)OrRuntime binding)Technology.Creating a virtual function with the virtual keyword can cause late bundling. The Compiler completes the necessary mechanism for late bundling.It creates a table (called

piece of code that can find the correct function body. This is called the late binding or runtime binding technology. 　 　Creating a virtual function with the virtual keyword can cause late bindingThe compiler completes the necessary mechanism for late bundling. It creates a table (vtable) for each class that contains virtual functions to place the address of the virtual function. In each class that contains virtual functions, the compiler secretly pl

Due to the recent company to develop a C + + plug-in mechanism-based, there is a major problem is C + + binary compatibility issues.Once the class uses the virtual function, as long as the random changes and additions and deletions to check the virtual function of the head file, it will cause the program to jump when running, because this time EXE and DLL inside the vtable model is inconsistentJust the program is developed using QT, so there are two w

A small Summary of undefined reference to vtable 1. Cause 1: The Destructor or constructor in the base class has no function implementation 2. cause 2: If your destructor has a function body but still reports this error, check whether it is an inline function definition. You can try to put the function implementation in. in the CPP file, do not place it in. h. 3. Cause 3: If none of the above are against .... Amount... I am so hard! In the end

Use eclipse to develop qt gui applications. If you want to customize a class, you need to use the signal/slot mechanism. Therefore, add it to the custom class.Q_objectMacro. However, an error is reported during build! Shape: Undefined reference to vtable I found the cause after checking on the Internet for a long time 《Qt causes of "undefined reference to 'vtable", But the solution is too oper

(1) Impact of vtable This increases the size of an object instance by 4 bytes. # Include # Include Using namespace STD; Class{Int;}; Class B{Virtual void say (){}Int B;}; Int main (INT argc, char * argv []){A;B;Cout Cout System ("pause ");Return exit_success;} Memset cannot be used for instances of objects containing virtual tables.The generation time and location of the virtual table are affected by placement new. # Include # Include Using namespa

for renaming an application.// ...... FN .................Farproc lpfn =: getprocaddress (HI, "fntrydll2 ");If (lpfn = NULL){Cout Return 0;}Lpfn ();// Farproc = int (* lpfn) (void)Typedef int (* lpfnp) (INT );Lpfnp = (lpfnp): getprocaddress (HI, "FNP ");If (lpfnp = NULL){Cout }Else{Lpfnp (15 );}// ...... Variable ................Int * Pi = (int *): getprocaddress (HI, "ntrydll2 ");If (Pi = NULL){Cout // Return 0;}// Ntrydll2 = 100; // The name cannot be changed even if the DLL is declared as ex

Class cbase{Public:Virtual void FN (){;}Virtual void add (cbase B){}Virtual void add (cbase Pb){} }; Class cpart: Public cbase{Public:Void FN (){Cout } }; Class ccom: Public cbase{Public:Void FN (){Cout Vector ITB = This-> m_vb.begin ();ITE = This-> m_vb.end ();//For (; ITB! = Ite; ++ ITB)(* ITB)-> (* ITB). FN ();}Void add (cbase B){M_vb.push_back (B );} Protected:Vector }; Int main (INT argc, char * argv []){Cpart P1, P2, P3, P4;Ccom C1, C2;Cbase * pb = P1;Pb-> FN ();PB = C1;Pb-> Add (P1 );Pb

, "ntrydll2 ");If (Pi = NULL){Cout // Return 0;}// ............... Class ........Ctrydll2 * PT = NULL;Farproc lpfn2 =: getprocaddress (HI, "getinstance ");If (lpfn2 = NULL){Cout Return 0;} // Note: the compilation link is correct.PT = (ctrydll2 *) lpfn2 ();Pt-> diplay (); // during execution, FNP (INT) in DLL is actually called. However, the runtime error occurs because the parameter is incorrect.Pt-> FNP (10); // during execution, display () in DLL is actually called. However, a runtime error o

Reference: http://www.weixueyuan.net/view/6372.htmlSummarize:In C + + through the virtual member function table vtable to achieve polymorphism, virtual function table is stored in the class virtual function of the entry address.Using polymorphism can reduce the efficiency of the program, use polymorphic programs to use more storage space, store virtual function tables and other content, and in the call function to go to the virtual function table to q

When using QT programming, when a user customizes a class, a signal or slot is used as long as the class.Code::Blocks compile will error (undefined reference to ' vtable for).There are many answers to this question on Google, but many of them are vague or not feasible at all.In fact, QT has its own method of compiling.Without the IDE writing a class, QT compiles the steps:1, CD source code directory2, Qmake-project3, Qmake Project_name.pro4, make (if

vtable/Reference and virtual function related, today in the addition of a layer of time reported this error, very low-level error, forgot to implement virtual function (remember!!) ）If the implementation of the virtual function is still the case, it may be created by the time you forget to hook up the-desktop option, the class is deleted once again add note hook on itCOCOS2D-X runtime Xcode hint error: "Vtable