Programming Forums > Application Development > C++

rwm · Jan 3rd, 2007, 5:03 AM

hi,

ive got a problem exporting template classes to dll...

for example, this works:

#define DllExport __declspec(dllexport)

class DllExport myClass {

	public:

		...

};

but this doesnt work

(Toggle Plain Text)

#define DllExport __declspec(dllexport)

template<typename T>
class DllExport myClass {

	public:

		...

};

i tried doing this:

(Toggle Plain Text)

typename myClass<int> myClassInt;

DllExport myClassInt;

doesnt work

are there any workarounds? can someone help me out here? i hope so!

thx

grumpy · Jan 3rd, 2007, 6:01 AM

The solution is compiler dependent (meaning you need to read your compiler documentation to be sure of the precise techiques) but is usually a variation of something like this ...... You would have to add the __declspec() prefix to the declaration of each member function in the class. And specialise the template within the DLL so it supplies and exports the classes (eg myclass<int>, myclass<double>, etc) that you intend to allow applications to employ.

In the end, it is usually easier to use the templates directly within applications that need them, than it is to attempt to supply all required specialisations in a DLL. Particularly as the DLL will only be usable from applications built with the same compiler as the DLL (thanks to the wonders of name mangling, and the fact that all compilers are strongly encouraged by the C++ standard to mangle function names in different ways).

rwm · Jan 8th, 2007, 2:51 AM

hey thx for the reply! sorry im replying late, been hecticly busy here!

umm, i dont quite understand what you getting at - can u give an example???

im using visual studio compiler

hope you can help!

thx!

Jan 3rd, 2007, 5:03 AM	#1
rwm Professional Programmer Join Date: Jan 2007 Location: Cape Town Posts: 291 Rep Power: 2	exporting template classes to DLL hi, ive got a problem exporting template classes to dll... for example, this works: (Toggle Plain Text) #define DllExport __declspec(dllexport) class DllExport myClass { public: ... }; #define DllExport __declspec(dllexport) class DllExport myClass { public: ... }; but this doesnt work (Toggle Plain Text) #define DllExport __declspec(dllexport) template<typename T> class DllExport myClass { public: ... }; #define DllExport __declspec(dllexport) template<typename T> class DllExport myClass { public: ... }; i tried doing this: (Toggle Plain Text) typename myClass<int> myClassInt; DllExport myClassInt; typename myClass<int> myClassInt; DllExport myClassInt; doesnt work are there any workarounds? can someone help me out here? i hope so! thx

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Jan 3rd, 2007, 6:01 AM	#2
grumpy Programming Guru Join Date: Jun 2005 Location: Adelaide, South Australia Posts: 1,254 Rep Power: 5	The solution is compiler dependent (meaning you need to read your compiler documentation to be sure of the precise techiques) but is usually a variation of something like this ...... You would have to add the __declspec() prefix to the declaration of each member function in the class. And specialise the template within the DLL so it supplies and exports the classes (eg myclass<int>, myclass<double>, etc) that you intend to allow applications to employ. In the end, it is usually easier to use the templates directly within applications that need them, than it is to attempt to supply all required specialisations in a DLL. Particularly as the DLL will only be usable from applications built with the same compiler as the DLL (thanks to the wonders of name mangling, and the fact that all compilers are strongly encouraged by the C++ standard to mangle function names in different ways).

Jan 8th, 2007, 2:51 AM	#3
rwm Professional Programmer Join Date: Jan 2007 Location: Cape Town Posts: 291 Rep Power: 2	hey thx for the reply! sorry im replying late, been hecticly busy here! umm, i dont quite understand what you getting at - can u give an example??? im using visual studio compiler hope you can help! thx!

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Programming Forums > Application Development > C++

exporting template classes to DLL