Re: Bison complains about undefined reference of my own data type

[Samuel Tardieu]

* Laurence Finston <address@hidden> [2008-11-28 15:48:02 +0100]

| > You need to do it to interface to any library written in C (such as
| > the standard C library for example). For example, try the following
| > C++ code with and without 'extern "C"'. Without it, you won't be able
| > to link. Fortunately, all your system headers already provide you with
| > 'extern "C"' by default.
| > 
| > extern "C" void exit(int);
| > int main()
| > {
| >   exit(0);
| > }
| 
| Thank you for the information.  However, I was able to compile and link
| with and without 'extern "C"' using GCC 3.3.3 on a system running 
| GNU/Linux (SuSE).  I couldn't link when I compiled with `g++' and tried 
| to link with `gcc', but the error didn't seem to have anything to do with 
| the problem under discussion:
| 
|    mangle.o(.eh_frame+0x11): undefined reference to `__gxx_personality_v0'
| 
| Am I missing something here? Clearly, `extern "C"' has a purpose, or it 
| wouldn't exist.  Does GCC do something special, or have I done something 
| wrong?

I wrote "this C++ code". It means that you must compile it with g++ (otherwise
it is valid C code), as well as link it with g++ (without deriving too much,
let me just say that g++ called in link mode does a bit more than linking --
it takes care of the exceptions, constructors and destructors as well through
another program called collect2).

| It seems to me that if a compiler doesn't mangle any "unqualified" names, 
| i.e., ones  declared outside of a namespace or a class, it should be possible 
to link
| with the object file in which they are defined without the linker having to 
| do anything special.  However, it's been a long time since I read
| anything about this subject and this may be naive.

The linker does nothing special wrt mangled names. Only the compiler does.