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From: ronen@cit-vax.Caltech.Edu (Ronen Barzel)
Newsgroups: comp.lang.c++
Subject: internal linkage for member functions?
Message-ID: <14373@cit-vax.Caltech.Edu>
Date: 22 Mar 90 02:07:59 GMT
Organization: California Institute of Technology
Lines: 61

C++ does not seem to allow "internal linkage" for member functions. 
Am I wrong -- is there a way to do it?  (If there isn't, IMHO there should be.)

Lippman sec 3.9 "static Global Variable" says:

    "A global identifier preceded by the keyword 'static' will be
     invisible outside the file in which it is defined...  Static
     identifiers at file scope are spoken of has having _internal_linkage_."

Preceding a declaration of a member function with 'static' isn't
covered by this.  If I try it, cfront gives an error

    "static specified for qualified name foo()"

-Ronen

[To answer the obvious question "why would you ever want to do that?",
 I'll describe the scenario in which I want it:

    I am writing a file to be included in a library; the file
    defines some user-callable functions.  Within that file,
    I declare a class with member functions; the class is only
    used internally by the library routines -- the user knows
    nothing about it.  Unfortunately, the mangled member function
    names get entered into the .o as global symbols.

	    // foo.H -- header file for "foo" library
	    extern void public_foo();

	    // foo.C -- implements "foo" library 
	    #include "foo.H"
	    class internal {
		public: func();
	    }
	    internal::func()  // want this to be 'static'
	    {
		// ...
	    }

	    void public_foo()
	    {
		internal x;
		x.func();
		// ...
	    }

    The symbol table for foo.o includes two global text symbols:
    "public_foo__Fv" (the one I want) and "func__8internalFv" (the
    one I want to get rid of).  I have two problems with this:

	1. I can't use the same class & member names in more than one
	   file in the library.  (A different file might want to define
	   a different 'internal' class with member function 'func'.)

	2. The extra symbols clutter up the .o file; aside from
	   being aestheticaly unappealing, on a large scale it will
	   lead to slower link times, etc.

    (Yes, the unwanted symbol can be removed via "ld -r -h func__8internalFv"
     or whatever is analogous on your platform, but that's sort of ugly.)
]