What Is the Purpose of _Cxa_Pure_Virtual

What is the purpose of __cxa_pure_virtual?

If anywhere in the runtime of your program an object is created with a virtual function pointer not filled in, and when the corresponding function is called, you will be calling a 'pure virtual function'.

The handler you describe should be defined in the default libraries that come with your development environment. If you happen to omit the default libraries, you will find this handler undefined: the linker sees a declaration, but no definition. That's when you need to provide your own version.

The infinite loop is acceptable because it's a 'loud' error: users of your software will immediately notice it. Any other 'loud' implementation is acceptable, too.

gcc undefined _cxa_pure_virtual

The lib in question is a C++ library and the __cxa_pure_virtual is needed by the C++ runtime. Suggest that you try first linking with g++ command instead of gcc.

Read more under this question: What is the purpose of cxa pure virtual

undefined symbol: __cxa_pure_virtual error when loading library from java

After rechecking all the answers related to my question on stackoverflow, I found out the answer by
Mark Seaborn to question: What is the purpose of __cxa_pure_virtual? fixed my problem.

As my jni library is managed by autotools, after adding "-Wl,--gc-sections -fPIC -shared -lstdc++" to AM_LDFLAGS of Makefile.am problems solved. libstdc++ might not necessary if code is compiled by a c++ compiler (e.g. g++).

Hope this could help others who have the same problem.

Linker errors when adding firebase framework to ios project

Sorry. We pushed a new version today that added a new dependency on libc++.dylib If you add that, it should build.

Note that there's also an issue with the current build that prevents building for arm64. Given that, you may want to just use the previous build: https://cdn.firebase.com/ObjC/Firebase.framework-1.0.9.zip

Else wait a day or so and we'll get the latest build straightened out.

Sorry for the inconvenience!

Where do pure virtual function call crashes come from?

They can result if you try to make a virtual function call from a constructor or destructor. Since you can't make a virtual function call from a constructor or destructor (the derived class object hasn't been constructed or has already been destroyed), it calls the base class version, which in the case of a pure virtual function, doesn't exist.

class Base
{
public:
    Base() { reallyDoIt(); }
    void reallyDoIt() { doIt(); } // DON'T DO THIS
    virtual void doIt() = 0;
};

class Derived : public Base
{
    void doIt() {}
};

int main(void)
{
    Derived d;  // This will cause "pure virtual function call" error
}

See also Raymond Chen's 2 articles on the subject

---

Related Topics