Re: [!! RANT !!] This is a hack at best (C4251)



Peter van der Goes wrote:

"Alfonso Morra" <sweet-science@xxxxxxxxxxxx> wrote in message news:dbt5jp$l9h$1@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

I cannot believe how convoluted it is to export function templates and class templates from a shared library (or DLL as it is called in the Windoze world).

Micro$oft support for STL and standards in general is absolutely appaling. This is absolutely ridiculous. I have obtaind links from people who tried to help me solve this problem, several days ago, to no avail. Even the sample code at http://support.microsoft.com/kb/q168958/ when adapted to my code (i.e. #defines specified etc), still generates compiler errors like:

error C2757: 'std' : a symbol with this name already exists and therefore this name cannot be used as a namespace name

This is from code provided by Microsoft. I TRULY HATE Microsoft (there I said it), and their non-standard, proprietary way of doing everything. I would not touch their flaky compilers if I did not have to work with them ...Arghhhh, I'm going out for a cofee break !


Perhaps when you return from your break, you'll provide some amplifying information about the problem you are having? That might make it possible for someone here to help you.


Hi peter,

Thanks for offering to help. This is really driving me round the bend. I have a little sample code below, which compiles and builds (with warnings). The built DLL exports the symbols, so I am not sure why the compiler issues the warnings (however, I have not tried to use the built DLL).

Here is the code:


using std::string ;
using std::vector ;

#ifdef TESTDLL_EXPORTS
#define CCONV __declspec(dllexport)
#else
#define CCONV __declspec(dllimport)
#endif

class CCONV MyClass {
public :
	MyClass():m_name("test"),val(0){} ;
	~MyClass(){} ;

	inline string getName( void ){ return m_name ; }
	inline void setName( string new_name ) { this->m_name = new_name ; }
	
	template <class T1, class T2>
	void foo( T1 arg1, T2 arg2 ) {
		;//dummy
	};
	
	inline vector<int> getDates( void ){ return dates ; }

private:
	//prevent copy and assignment
	MyClass( const MyClass& ) ;
	MyClass& operator=(const MyClass&) ;

	/* Nested class */
	class MyNestEgg {
		friend class MyClass ;
		void doThis(void){;}
		void doThat(void){;}
	};

	string		m_name ;
	int			val ;
	MyNestEgg	m_nuts ;
	vector<int>	dates ;

public:
	inline void doThisToMyNestEgg( void ) { m_nuts.doThis() ; }
	inline void doThatToMyNestEgg( void ) { m_nuts.doThis() ; }

};



Two thing I must mentioned however, are:

1). I notice that the compiler does not complain about the myNestEgg variable. In my actual code, the compile complains as ff:
"warning C4251: 'A::m_props' : class 'A::Properties' needs to have dll-interface to be used by clients of class 'A'

2). The function template is completely ignored and not even exported. This is not too suprising since it may require template specialiazation - but this is only a guess, siince I cannot find anything useful on Microsoft's site - and the code given there to allow exporting STL objects from a shlib does not work.


I hope you can provide a fix as to how to get this to work (i.e. compile without warnings and to export STL classes). The actual code I have inherits from a template class like this:

MyClass: public Singleton<MyClass> { ...}

For now, i want to keep things simple, and I will discuss that once I have managed to get the simple class (i.e. with no inheritance extensions) to compile and export symbols correctly.

MTIA

.

Relevant Pages

  • Re: disable reading of asp pages
    ... Don't put your CodeBehind class code in the Page template, ... compile it into a DLL. ... the Page Template will use the compiled DLL instead. ...
    (microsoft.public.dotnet.framework.aspnet)
  • Re: umm... something... template(s)... something else... pointer(s)... and such... 0.o yah, Im hopel
    ... It doesn't make sense to try an put a template in a DLL, ... only instantiations of templates are object code. ... ahead of time (when you compile the DLL). ...
    (comp.lang.cpp)
  • Re: Visual C++ 6.0 DLL question
    ... This method works fine and dandy for regular classes, but what about template ... I found a template class has to be all in the header ... Now I want to include a few template classes in my DLL. ... I go to compile it and the DLL is generated but not LIB or EXP files ...
    (microsoft.public.vc.language)
  • Re: [!! RANT !!] This is a hack at best (C4251)
    ... The template function won't be generated until it's instantiated. ... really cannot export template functions from a DLL. ... templatevoid foo ... the compile complains as ff: ...
    (microsoft.public.dotnet.languages.vc)
  • Re: STL error
    ... > application DLL that I have a template for it which is based on STL. ... Is it related to the way that I setup my MSVC? ...
    (microsoft.public.vc.stl)