GCC: Simple inheritance test fails

Question

I'm building an open source 2D game engine called YoghurtGum. Right now I'm working on the Android port, using the NDK provided by Google.

I was going mad because of the errors I was getting in my application, so I made a simple test program:

class Base
{

public:

    Base() { }
    virtual ~Base() { }


}; // class Base

class Vehicle : virtual public Base
{

public:

    Vehicle() : Base() { }
    ~Vehicle() { }


}; // class Vehicle

class Car : public Vehicle
{

public:

    Car() : Base(), Vehicle() { }
    ~Car() { }

}; // class Car

int main(int a_Data, char** argv)
{
    Car* stupid = new Car();

    return 0;
}

Seems easy enough, right? Here's how I compile it, which is the same way I compile the rest of my code:

/home/oem/android-ndk-r3/build/prebuilt/linux-x86/arm-eabi-4.4.0/bin/arm-eabi-g++
-g 
-std=c99 
-Wall 
-Werror 
-O2 
-w 
-shared 
-fshort-enums 
-I ../../YoghurtGum/src/GLES 
-I ../../YoghurtGum/src 
-I /home/oem/android-ndk-r3/build/platforms/android-5/arch-arm/usr/include 
-c src/Inheritance.cpp 
-o intermediate/Inheritance.o

(Line breaks are added for clarity). This compiles fine. But then we get to the linker:

/home/oem/android-ndk-r3/build/prebuilt/linux-x86/arm-eabi-4.4.0/bin/arm-eabi-gcc
-lstdc++ 
-Wl,
--entry=main,
-rpath-link=/system/lib,
-rpath-link=/home/oem/android-ndk-r3/build/platforms/android-5/arch-arm/usr/lib,
-dynamic-linker=/system/bin/linker,
-L/home/oem/android-ndk-r3/build/prebuilt/linux-x86/arm-eabi-4.4.0/lib/gcc/arm-eabi/4.4.0,
-L/home/oem/android-ndk-r3/build/platforms/android-5/arch-arm/usr/lib,
-rpath=../../YoghurtGum/lib/GLES 
-nostdlib 
-lm 
-lc 
-lGLESv1_CM  
-z 
/home/oem/android-ndk-r3/build/platforms/android-5/arch-arm/usr/lib/crtbegin_dynamic.o 
/home/oem/android-ndk-r3/build/platforms/android-5/arch-arm/usr/lib/crtend_android.o
intermediate/Inheritance.o 
../../YoghurtGum/bin/YoghurtGum.a 
-o bin/Galaxians.android

As you can probably tell, there's a lot of cruft in there that isn't really needed. That's because it doesn't work. It fails with the following errors:

intermediate/Inheritance.o:(.rodata._ZTI3Car[typeinfo for Car]+0x0): undefined reference to `vtable for __cxxabiv1::__si_class_type_info'
intermediate/Inheritance.o:(.rodata._ZTI7Vehicle[typeinfo for Vehicle]+0x0): undefined reference to `vtable for __cxxabiv1::__vmi_class_type_info'
intermediate/Inheritance.o:(.rodata._ZTI4Base[typeinfo for Base]+0x0): undefined reference to `vtable for __cxxabiv1::__class_type_info'
collect2: ld returned 1 exit status
make: *** [bin/Galaxians.android] Fout 1

These are the same errors I get from my actual application.

If someone could explain to me where I went wrong in my test or what option or I forgot in my linker, I would be very, extremely grateful.

Thanks in advance.

UPDATE:

When I make my destructors non-inlined, I get new and more exciting link errors:

intermediate/Inheritance.o:(.rodata+0x78): undefined reference to `vtable for __cxxabiv1::__si_class_type_info'
intermediate/Inheritance.o:(.rodata+0x90): undefined reference to `vtable for __cxxabiv1::__vmi_class_type_info'
intermediate/Inheritance.o:(.rodata+0xb0): undefined reference to `vtable for __cxxabiv1::__class_type_info'
collect2: ld returned 1 exit status
make: *** [bin/Galaxians.android] Fout 1

Answer 1

Use g++ to drive the linker, not gcc:

/home/oem/android-ndk-r3/build/prebuilt/linux-x86/arm-eabi-4.4.0/bin/arm-eabi-g++
-Wl,
--entry=main,
...

Update: another problem appears to be your use use of -nostdlib. This is stopping the compiler from adding all the standard libraries (such as the runtime library that provides your missing externals). Is there a reason you need this?

Answer 2

You tried to instantiate in your initialization list a base you didn't inherit from. Car only inherits from Vehicle and not also Base. From your code I assume that was your intention.

I personally prefer to use composition rather than multiple inheritance - it's cleaner and better performance.

Answer 3

To quote from http://gcc.gnu.org/faq.html#vtables

"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 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." [Emphasis mine]

If you just make your virtual destructors non-inline that should fix the problem.