questions about name mangling in C++

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C does not do name mangling, though it does pre-pend an underscore to function names, so the printf(3) is actually _printf in the libc object.

In C++ the story is different. The history of it is that originally Stroustrup created “C with classes” or cfront, a compiler that would translate early C++ to C. Then rest of the tools – C compiler and linker would we used to produce object code. This implied that C++ names had to be translated to C names somehow. This is exactly what name mangling does. It provides a unique name for each class member and global/namespace function and variable, so namespace and class names (for resolution) and argument types (for overloading) are somehow included in the final linker names.

This is very easy to see with tools like nm(1) – compile your C++ source and look at the generated symbols. The following is on OSX with GCC:

namespace zoom
{
    void boom( const std::string& s )
    {
        throw std::runtime_error( s );
    }
}

~$ nm a.out | grep boom
0000000100001873 T __ZN4zoom4boomERKSs

In both C and C++ local (automatic) variables produce no symbols, but live in registers or on stack.

Edit:

Local variables do not have names in resulting object file for mere reason that linker does not need to know about them. So no name, no mangling. Everything else (that linker has to look at) is name-mangled in C++.

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