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smeyers@netcom.com (Scott Meyers) writes:

>I'm a little confused about the meaning of extern inline functions.
>DWP 7.1.1.4 makes it clear that extern inline functions have external
>linkage, so I have two questions.
>
>1.  Suppose this definition occurs in header1.h:
>
>      extern inline f() { cout << "Hello."; }
>    
>    Further suppose that header1.h is #included by file1.cpp, file2.cpp, and
>    file3.cpp and that, for whatever reason, f is NOT inlined.  Which object
>    file will contain the definition of f?  My understanding is that only
>    one of them will.

The C++ standard does not define the notion of an "object file".
Not all implementations use object files.  (For example, C++ interpreters
may just load the source files into memory.)

However, I think typical implementations will place a definition of f()
in every object file, and then merge them at link time to ensure that
the final executable only contains one definition of f().

If you want to find out what your particular implementation does, try
compiling to assembler (often the `-S' compiler option will have this
effect) and examining the assembler file, or try exaxmining the object
file (on Unix implementations, you can use the `nm' command to do
this).

>2.  Now suppose there is a second header file header2.h, which contains
>    this definition:
>
>      extern inline f() { cout << "Goodbye."; }  // note that this is
>                                                 // not the same as f above
>
>    If I link together an object file containing the definition of f
>    from header1.h and another object file containing the definition of
>    f from header2.h, am I correct in assuming that the resulting
>    program violates the one definition rule and that this violation
>    need not be diagnosed?

Yes.

--
Fergus Henderson             	WWW: http://www.cs.mu.oz.au/~fjh
fjh@cs.mu.oz.au              	PGP: finger fjh@128.250.37.3
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