Error C2491 Definition Of Dllimport
Contents |
here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site About Us Learn more about Stack Overflow the company Business error c2491 definition of dllimport function not allowed Learn more about hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation error c2491 definition of dllimport static data member not allowed Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like a function declared dllimport may not be defined you, helping each other. Join them; it only takes a minute: Sign up C++ definition of dllimport static data member up vote 14 down vote favorite 4 I do have a class which looks like below: //.h definition of dllimport function not allowed visual studio file class __declspec(dllimport) MyClass { public: //stuff private: static int myInt; }; // .cpp file int MyClass::myInt = 0; I get the following compile error: error C2491: 'MyClass::myInt' : definition of dllimport static data member not allowed what should I do? c++ dll static static-members share|improve this question asked Aug 16 '10 at 9:34 MBZ 5,6301767133 add a comment| 3 Answers 3 active oldest votes up vote 19 down vote accepted __declspec(dllimport) means that the
Definition Of Dllimport Static Data Member Not Allowed Qt
current code is using the DLL that implements your class. The member functions and static data members are thus defined in the DLL, and defining them again in your program is an error. If you are trying to write the code for the DLL that implements this class (and thus defines the member functions and static data members) then you need to mark the class __declspec(dllexport) instead. It is common to use a macro for this. When building your DLL you define a macro BUILDING_MYDLL or similar. In your header for MyClass you then have: #ifdef BUILDING_MYDLL #define MYCLASS_DECLSPEC __declspec(dllexport) #else #define MYCLASS_DECLSPEC __declspec(dllimport) #endif class MYCLASS_DECLSPEC MyClass { ... }; This means that you can share the header between the DLL and the application that uses the DLL. share|improve this answer answered Aug 16 '10 at 9:58 Anthony Williams 40.7k586126 Here is the corresponding cite on Microsoft's page: "Using __declspec(dllimport) is optional on function declarations [...]. However, you must use __declspec(dllimport) for the importing executable to access the DLL's public data symbols and objects. Note that the users of your DLL still need to link with an import library." –Jonny Dee Oct 9 '14 at 11:04 add a comment| up vote 2 down vote From MSDN Documentation, When you declare a class dllimport, all its member functions and static data members
here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site About Us Learn more about Stack Overflow the company Business Learn more about hiring
Definition Of Dllimport Function Not Allowed Template
developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question cannot define dllimport entity c++ x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. Join error c2491: 'round': definition of dllimport function not allowed them; it only takes a minute: Sign up C++ definition of dllimport static data member up vote 14 down vote favorite 4 I do have a class which looks like below: //.h file class __declspec(dllimport) MyClass { public: //stuff private: http://stackoverflow.com/questions/3491990/c-definition-of-dllimport-static-data-member static int myInt; }; // .cpp file int MyClass::myInt = 0; I get the following compile error: error C2491: 'MyClass::myInt' : definition of dllimport static data member not allowed what should I do? c++ dll static static-members share|improve this question asked Aug 16 '10 at 9:34 MBZ 5,6301767133 add a comment| 3 Answers 3 active oldest votes up vote 19 down vote accepted __declspec(dllimport) means that the current code is using the DLL that implements your class. The member http://stackoverflow.com/questions/3491990/c-definition-of-dllimport-static-data-member functions and static data members are thus defined in the DLL, and defining them again in your program is an error. If you are trying to write the code for the DLL that implements this class (and thus defines the member functions and static data members) then you need to mark the class __declspec(dllexport) instead. It is common to use a macro for this. When building your DLL you define a macro BUILDING_MYDLL or similar. In your header for MyClass you then have: #ifdef BUILDING_MYDLL #define MYCLASS_DECLSPEC __declspec(dllexport) #else #define MYCLASS_DECLSPEC __declspec(dllimport) #endif class MYCLASS_DECLSPEC MyClass { ... }; This means that you can share the header between the DLL and the application that uses the DLL. share|improve this answer answered Aug 16 '10 at 9:58 Anthony Williams 40.7k586126 Here is the corresponding cite on Microsoft's page: "Using __declspec(dllimport) is optional on function declarations [...]. However, you must use __declspec(dllimport) for the importing executable to access the DLL's public data symbols and objects. Note that the users of your DLL still need to link with an import library." –Jonny Dee Oct 9 '14 at 11:04 add a comment| up vote 2 down vote From MSDN Documentation, When you declare a class dllimport, all its member functions and static data members are imported. Unlike the behavior of dllimport and dllexport on nonclass types, static data members cannot specify a definition in the same
here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site About http://stackoverflow.com/questions/7657552/definition-of-dllimport-function-not-allowed Us Learn more about Stack Overflow the company Business Learn more about hiring http://stackoverflow.com/questions/17239506/c-definition-of-dllimport-function-not-allowed-building-with-visual-studio-2 developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up definition of dllimport function not allowed definition of up vote 3 down vote favorite While compiling a C code, I'm getting the following error: c:\users\kbarman\documents\mser\vlfeat-0.9.13-try\mser\stringop.c(71): error C2491: 'vl_string_parse_protocol' : definition of dllimport function not allowed In the file stringop.c, I have the following function: VL_EXPORT char * vl_string_parse_protocol (char const *string, int *protocol) { char const * cpt ; int dummy ; /* handle the case prot = 0 */ if (protocol == 0) definition of dllimport protocol = &dummy ; /* look for :// */ cpt = strstr(string, "://") ; if (cpt == 0) { *protocol = VL_PROT_NONE ; cpt = string ; } else { if (strncmp(string, "ascii", cpt - string) == 0) { *protocol = VL_PROT_ASCII ; } else if (strncmp(string, "bin", cpt - string) == 0) { *protocol = VL_PROT_BINARY ; } else { *protocol = VL_PROT_UNKNOWN ; } cpt += 3 ; } return (char*) cpt ; } And VL_EXPORT is defined as follows: # define VL_EXPORT extern "C" __declspec(dllimport) Can somebody please tell me what is causing this error and how I can get rid of it? c dllimport share|improve this question asked Oct 5 '11 at 6:37 user979791 16112 Look up from that #define, there's a #ifdef that selects between dllexport and dllimport. You need dllexport here so define that macro. –Hans Passant Oct 5 '11 at 8:38 add a comment| 2 Answers 2 active oldest votes up vote 3 down vote As documentation states, dllimport function are not allowed to have a body right there. [...] functions can be declared as dllimports but not defined as dllimports. // function definition void __declspec(dllimport) fu
here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site About Us Learn more about Stack Overflow the company Business Learn more about hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up c++: definition of dllimport function not allowed, building with visual studio 2010 up vote 8 down vote favorite 2 I'm using visual studio 2010 to build a .dll. I wrote up a trial as: // trialDLL.h #ifndef TRIALDLL_H_ #define TRIALDLL_H_ // ... MyMathFuncs class definition omitted #ifdef __cplusplus extern "C"{ #endif #ifdef TRIALDLL_EXPORT #define TRIALDLL_API __declspec(dllexport) #else #define TRIALDLL_API __declspec(dllimport) #endif TRIALDLL_API MyMathFuncs* __stdcall new_MyMathFuncs(double offset); TRIALDLL_API void __stdcall del_MyMathFuncs(MyMathFuncs *myMath); TRIALDLL_API double __stdcall MyAdd(MyMathFuncs* myMath, double a, double b); // some other similar stuff #ifdef __cplusplus } #endif #endif And the triallDLL.cpp file: // trialDLL.cpp #include "trialDLL.h" TRIALDLL_API MyMathFuncs* __stdcall new_MyMathFuncs(double offset) { return new MyMathFuncs(offset); } TRIALDLL_API void __stdcall del_MyMathFuncs(MyMathFuncs *myMath) { delete myMath; } TRIALDLL_API double __stdcall MyAdd(MyMathFuncs *myMath, double a, double b) { return myMath->Add(a, b); } // ... some other definitions With these two files in the project, I added a property sheet to the project through visual studio 2010 property manager and added TRIALDLL_EXPORT to user macros. After all these, the nice Intellisense gives me error for each function defined in the .cpp file and com