Re: unexpected public symbol in .obj for inlined function

From:
Ulrich Eckhardt <eckhardt@satorlaser.com>
Newsgroups:
microsoft.public.vc.language
Date:
Tue, 23 Oct 2007 16:38:47 +0200
Message-ID:
<ukd1v4-pu3.ln1@satorlaser.homedns.org>
Mario Semo wrote:

usually the compiler generates no symbol in the symbol table for an
inlined member.


Not so, see the thread "inline functions are reported as weak symbols in .o
file ( by nm - marked as W )" in comp.lang.c++.moderated.

inline int DerivedClass::function()
{
 return 0;
}

But this is not the case in the following sample.
(See below).
where a public (external) symbol is generated.

A problem occurs when the above inline function is included in 2
independent .cpp files and both .obj files are linked together (e.q. into
a dll).

======== ExportTst1.cpp =======
class BaseClass
{
 public:
   virtual int function()
   {
    return 123;
   }

};

class DerivedClass
: public BaseClass
{
 public:
   virtual inline int function();
};

template <class Base>
class TemplClass
: public DerivedClass
{
 public:
    int callFunction();

    static inline Base & BaseOf(TemplClass<Base> const &);
    static Base * b;
};

template <class Base>
Base * TemplClass<Base>::b = 0;

template <class Base>
int TemplClass<Base>::callFunction()
{
 return BaseOf(*this).Base::function();
}

template <class Base>
inline Base & TemplClass<Base>::BaseOf(TemplClass<Base> const &)
{
 return *b;
}

inline int DerivedClass::function()
{
 return 0;
}

template TemplClass<DerivedClass>;


I'm not 100% sure if that is what is biting you here, but I found that if I
derive from a template and export that class from a DLL, it also exports
the (otherwise inline) members of the baseclass. I personally consider that
a bug, but in a discussion there were also some other opinions.

However, here you only have the same inline function compiled twice in the
same executable ... I wonder, what exactly is the errormessage?

Note : The Problem flushes when the last statement
template TemplClass<DerivedClass>;
is removed. But i need the explizit template instantation. The original
code is splitted into multiple files (the inline function are in a .inl
file, the template functions are in a .c file, the classes/templates in a
.hpp and the templ. instance is a client.cpp file).


Hmmm, what is the difference between the content of the .inl file and the .c
file? Also, just to make sure, MSVC treats all .c files as C code and not
C++!

Uli

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