c++ - undefined reference to and non-virtual thunk to

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Closed 10 years ago .

And I have those errors:

/home/katie/Desktop/Temp/MusicStore.cpp||In member function ‘virtual bool  MusicStore::hasProduct( Product)’:|
/home/katie/Desktop/Temp/MusicStore.cpp|15|warning: no return statement in function returning non-void [-Wreturn-type]|
/home/katie/Desktop/Temp/MusicStore.cpp||In member function ‘virtual  Product  MusicStore::getProduct( Product)’:|
/home/katie/Desktop/Temp/MusicStore.cpp|20|warning: no return statement in function returning non-void [-Wreturn-type]|
/home/katie/Desktop/Temp/MusicStore.cpp||In member function ‘virtual bool  MusicStore::buyProduct( Product)’:|
/home/katie/Desktop/Temp/MusicStore.cpp|25|warning: no return statement in function returning non-void [-Wreturn-type]|
/home/katie/Desktop/Temp/MusicStore.cpp||In member function ‘virtual bool  MusicStore::returnProduct( Product)’:|
/home/katie/Desktop/Temp/MusicStore.cpp|30|warning: no return statement in function returning non-void [-Wreturn-type]|
/home/katie/Desktop/Temp/Store/CD.cpp||In member function ‘virtual void  CD::setAuthor(std::string)’:|
/home/katie/Desktop/Temp/Store/CD.cpp|12|warning: label ‘MusicProduct’ defined but not used [-Wunused-label]|
obj/Debug/Store/CD.o:(.rodata._ZTVN5Music2CDE[vtable for  CD]+0x10)||undefined reference to ` CD::getPrice()'|
obj/Debug/Store/CD.o:(.rodata._ZTVN5Music2CDE[vtable for  CD]+0x14)||undefined reference to ` CD::setPrice(double)'|
obj/Debug/Store/CD.o:(.rodata._ZTVN5Music2CDE[vtable for  CD]+0x20)||undefined reference to `non-virtual thunk to  CD::getPrice()'|
obj/Debug/Store/CD.o:(.rodata._ZTVN5Music2CDE[vtable for  CD]+0x24)||undefined reference to `non-virtual thunk to  CD::setPrice(double)'|
obj/Debug/Store/CD.o:(.rodata._ZTIN5Music2CDE[typeinfo for  CD]+0x10)||undefined reference to `typeinfo for  MusicProduct'|
obj/Debug/Store/CD.o:(.rodata._ZTIN5Music2CDE[typeinfo for  CD]+0x18)||undefined reference to `typeinfo for  Product'|
||=== Build finished: 6 errors, 5 warnings ===|
What is wrong with this code?
Besides the missing CD:: qualifier error mentioned by momogentoo, this is another very sneaky error:
void CD::setAuthor(string author)
    MusicProduct:author = author; // <-- !!!
Since you used a single colon, it isn't interpreted as the resolution operator, but as a label (for gotos). What the statement will actually do is just self-assignment for the same string object (which for std::string will have no effect).
                Just hit this error message. Never figured it out and it went away with a make clean, so I guess just stale object files.
– jozxyqk
                Aug 13, 2014 at 10:39
Your definition of that function is missing the CD:: qualification; so it instead declares and defines a non-member function.
double CD::getPrice()
{//    ^^^^ Add this
MusicProduct::price = price;
Likewise for CD::setPrice.
Second problem:
undefined reference to `typeinfo for  MusicProduct'
Presumably, MusicProduct is supposed to be an abstract class, and you don't want to provide definitions for its virtual functions. In that case, you must declare them pure virtual:
virtual double getPrice() = 0;
//                        ^^^ Add this
If it's not supposed to be abstract, then you'll need to implement those functions.
Third problem:
In member function ‘virtual bool  MusicStore::hasProduct( Product)’:
warning: no return statement in function returning non-void [-Wreturn-type]
Presumably, you have a function called MusicStore::hasProduct which is supposed to return a boolean, but doesn't.
                if I implement methods from Product class as pure virtual, I wont be able to do this: class MusicStore{ public: void addProduct(Product p);}; is there any way to solve this?
– Katie
                Feb 4, 2013 at 14:58
                @Katie: If you want to use polymorphism at all, then you'll have to pass a reference (Product & p) or pointer (Product * p). Even if it weren't abstract, trying to copy it will almost certainly give incorrect behaviour due to the slicing problem; so it's better to leave the base class abstract and not try to copy objects.
– Mike Seymour
                Feb 4, 2013 at 15:01