Question

I’d like to create a dll library from C++ code and use it in C program. I’d like to export only one function:

GLboolean load_obj (const char *filename, GLuint &object_list); 

Header file from library:

#ifndef __OBJ__H__ #define __OBJ__H__  #include <windows.h>   #include <GL/gl.h> #include <GL/glext.h> #include <GL/glu.h> #include <GL/glut.h>  #if defined DLL_EXPORT #define DECLDIR __declspec(dllexport) #else #define DECLDIR __declspec(dllimport) #endif  extern 'C' GLboolean load_obj (const char *filename, GLuint &object_list);  #endif // __3DS__H__ 

in .cpp (in library project) function is also declared as:

extern 'C' GLboolean load_obj (const char *filename, GLuint &object_list) {  code... } 

File .lib is added in VS project options (Linker/Input/Additional dependencies). .dll is in folder where .exe is. When I compile C project – error:

Error   1   error C2059: syntax error : 'string'     

It is about part ‘extern ‘C’ ‘ in header file.

I’ve tried to change header file to:

extern GLboolean load_obj (const char *filename, GLuint &object_list); 

then

Error   1   error C2143: syntax error : missing ')' before '&'   Error   2   error C2143: syntax error : missing '{' before '&'   Error   3   error C2059: syntax error : '&'  Error   4   error C2059: syntax error : ')'  

and even when I changed & to * appeared:

Error   6   error LNK2019: unresolved external symbol _load_obj referenced in function _main    main.obj     

I’ve no idea why it is wrong. .lib .h and .dll are properly added.

Answer 1

The parameter ‘GLuint &object_list‘ means ‘pass a reference to an GLuint here’. C doesn’t have references. Use a pointer instead.

// declaration extern 'C' GLboolean load_obj (const char *filename, GLuint *object_list);  // definition GLboolean load_obj (const char *filename, GLuint *object_list) {     code... }