Error Undefined Symbol Virtual Table For Class
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The First Non-inline Virtual Member Function Has No Definition
I am porting a game from windows to mac. Here I am stuck with a bunch of linker errors. All errors similar to Undefined symbols "typeinfo for Baseclass", referenced from: typeinfo for Subclass Subclass.oor "vtable for Aclass referenced from _ZTVNAclass:` I know that the problem because of missing definition for virtual functions. Its big project and difficult to trace undefined virtual functions. Is their any way to quickly identify undefined virtual functions. vtable for referenced from Why cant the compiler identify undefined virtual functions and give a meaningful message instead of cryptic vtable message. Minimal example :- class Foo { public: virtual ~Foo(){}; virtual void someMethod(); }; int main() { Foo foo; return 0; } And g++ version 4.2.1 (Apple Inc. build 5664) says:- Undefined symbols: "vtable for Foo", referenced from: Foo::Foo() in ccj8yYI2.o ld: symbol(s) not found collect2: ld returned 1 exit status c++ oop share|improve this question edited Feb 11 '15 at 10:58 Michael Haidl 3,5311026 asked Sep 7 '10 at 11:06 shakthi 717924 2 BEcause if the error messages were easy to read anybody could program and then we would not get the huge salaries that we currently get for being able to decrypt these messages :-) Its a job security thing. –Loki Astari Sep 7 '10 at 11:29 Nothing sensible comes to my mind. Was in the same boat once. Probably only piping the linker output via c++filt might help a bit by demangling C++ names. One can also try to peek the symbol tables of .o files with the nm, somehow filtering the symbols which are defined (and symbols from standard libraries). That would leave you with a list of undefined symbols. 20+ lines in Perl/friends. –Dummy00001 Sep 7 '10
for Foo", referenced from: Foo::Foo() in ccqNJSZ0.o ld: symbol(s) not found for architecture x86_64 collect2: ld returned 1 exit status It means you have declared virtual functions but you haven't defined any of them non-inline. Here's the undefined symbols for architecture x86_64: "vtable for code that caused this: class Foo { virtual void f(); }; int main(int argc, char
Undefined Symbol Typeinfo For Class
**argv) { Foo foo; return(0); } Now, it's true that you would expect a linkage error here, but not this linkage error. Rather,
Undefined Symbol Vtable For Class
you'd appear to get a complaint about function f() being missing, which is what happens when you change the class definition a bit to have f() defined but b() undefined. class Foo { virtual void f(); virtual void http://stackoverflow.com/questions/3658072/how-to-find-undefined-virtual-functions-of-a-classes b(); }; void Foo::f() {} This gives the expected error: Undefined symbols for architecture x86_64: "Foo::b()", referenced from: vtable for Fooin ccxuo26H.o ld: symbol(s) not found for architecture x86_64 What's going on here is described in a GCC FAQ entry: The ISO C++ Standard specifies that all virtual methods of a class that are not pure-virtual must be defined, but does not require any diagnostic for violations of this rule [class.virtual]/8. Based on this assumption, GCC will http://www.educatedguesswork.org/2011/09/undefined_symbol_vtable_what_t.html only emit the implicitly defined constructors, the assignment operator, the destructor and the virtual table of a class in the translation unit that defines its first such non-inline method. Therefore, if you fail to define this particular method, the linker may complain about the lack of definitions for apparently unrelated symbols. Unfortunately, in order to improve this error message, it might be necessary to change the linker, and this can't always be done. Pretty sweet, huh? Categories: Software 2 Comments By Steve Checkoway on September 3, 2011 1:17 AM The symbol it's complaining about isn't unrelated, it is the vtable for Foo, after all (__ZTV3Foo on Mac OS X, probably _ZTV3Foo on Linux since Linux doesn't typically decorate symbols with leading underscores). A little experimentation shows that the translation unit that contains the definition of the first, noninline virtual function gets the vtable and the type info. Consider the following: // a.h class Foo { virtual void f(); virtual void b(); }; // a.cc #include "a.h" void Foo::f() {} // b.cc #include "a.h" void Foo::b() {} // c.cc #include "a.h" Foo foo; If you compile a.cc, b.cc, and c.cc and take a look at the symbols of each, you see that a.o defines symbols __ZN3Foo1fEv (which, unfortunately, I can read without c++filt *sigh*), __ZTI3Foo, __ZTS3Foo, and __ZTV3Foo--Foo::f(void), typeinfo for Foo, typeinfo name for Foo, and vtable fo
NON-RTTI OBJECT AIX Subscribe You can track all active APARs for this component. APAR status Closed as user error. Error description PMR: 31253.379.000 Product: VAC++ 5.0.2 Platform: AIX 4.3 . The testcase bellow fails to http://www.ibm.com/support/docview.wss?uid=swg1IY26210 compile if main module (main.cpp) is compiled with option -qrtti and libmy.a without. Compiler http://thinkingeek.com/2012/08/08/common-linking-issues-c/ generates several warnings and a linker error: . $ xlC -qrtti=all -I. -c main.cpp $ xlC -qmkshrobj -I. -o libmy.a libmy.cpp $ xlC main.o -L. -lmy ld: 0711-224 WARNING: Duplicate symbol: .A::f() ld: 0711-224 WARNING: Duplicate symbol: .A::g() ld: 0711-224 WARNING: Duplicate symbol: A::g() ld: 0711-224 WARNING: Duplicate symbol: A::f() ld: 0711-345 Use the -bloadmap or -bnoquiet option to undefined symbol obtain mor information. ld: 0711-317 ERROR: Undefined symbol: Virtual table for class "D": first non-inline virtual function in "D" is not defined. . If both objects are compiled without -qrtti or if virtual inheri not used, the testcase compiles fine. . B1 B2 | | (v)----+----(v) | A | D . Testcase: =========== . ////// libmy.h ///////// #ifndef _LIBMY_H_ #define _LIBMY_H_ class B1{ public: virtual int g(){ return 1; } }; class A : undefined symbol vtable virtual public B1, virtual public B2{ public: virtual int f(){ return 1; } virtual int g(){ return 1; } }; class D : public A{ public: virtual int f(); virtual int g(); }; #endif /*_LIBMY_H_*/ ///////// libmy.cpp ///////// #include
at declaring stuff but not defining it. Declaring something in C++ means bringing the entity into existence in the program, so it can be used after the declaration point. Defining something means giving a complete description of the entity itself. You can declare a class or a function, and it means this class and this function do exist. But to completely describe a class and a function you have to define them. A class definition provides a list of base classes of that class, a list of members (data members and member functions) of that class, etc. A function definition provides the executable code of that function. All definitions are declarations but not all declarations are definitions. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 // Defines variable 'x' int x; // Declares variable 'y' extern int y; // Declares class 'A' struct A; // Declares function 'f(int)' void f(int); // Defines class 'A' struct A { // Declares member function 'A::g(float)' void g(float); // Defines member function 'A::h(char)' void h(char) { // Code } // Defines data member 'A::x' int x; // Declares static data member 'A::y' static int y; }; // Defines function'f(int)' void f(int) { // Code } // Defines member function 'A::g(float)' void A::g(float) { // Code } // Defines static data member 'A::y' int A::y; C++, in contrast to C, strongly sticks to the One Definition Rule which states that entities can be defined at most once in an entire program. Of course this may not be completely true depending your own the definition of "entity": template functions when instantiated by the compiler can be defined more than once in the program, and some magic happens so this does not become a problem. Anyway, C++ brings its own set of link