C to C++ link error

[jimNLX]

I'm trying to convert a C program into a VC++ program and have everything compiling but I get a ton of Link errors. The error I get is: error LNK2005: ... already defined in ... I'm getting 230+ of these error and don't really know why. I've used #pragam once in all the headers, but still get this error. Any help on this error or converting C to C++? Thanks, Jim

[Joaquin M Lopez Munoz]

Does the symbol correspond to a global variable? Something like this?

int global;

If so, try writing this in the .h file:

extern int global;

and then this in just one .cpp:

int global=0;

If this works and you're curious, I can try to explain the reason of your problem. Joaquín M López Muñoz Telefónica, Investigación y Desarrollo

[jimNLX]

It's defined in a header with the extern key word.

[jimNLX]

Here is what is defined in the header file: #ifdef ELABORATE_ALL_VARIABLES D2N_GLBL_STRUCT *D2N_GLBL; void D2N_GLBL_Elab( void ); void D2N_GLBL_Elab( void ) { D2N_GLBL = (D2N_GLBL_STRUCT *) calloc( sizeof(D2N_GLBL_STRUCT), 1); } #else extern D2N_GLBL_STRUCT *D2N_GLBL; #endif

[Joaquin M Lopez Munoz]

remove extern D2N_GLBL_STRUCT *D2N_GLBL;

??????? What is that remove thing? Could you explain what this file (is it a header?) is supposed to do, and what role does the macro ELABORATE_ALL_VARIABLES play? Joaquín M López Muñoz Telefónica, Investigación y Desarrollo

[jimNLX]

I wish I knew, but I've never seen the program run before! I'm just having to port it to C++. The remove was something I forgot to remove when debugging. I think that this Macro does two different things based on what function is using it.

[Joaquin M Lopez Munoz]

Ok. We can try to make an educated guess :) My opinion is that the header is used both for declaring things and for defining them. The second use is activated by ELABORATE_ALL_VARIABLES. Let's say the header is called a.h: then I guess you have to #include it like always everywhere except in the one file a.cpp, where you should have to write:

// a.cpp
#define ELABORATE_ALL_VARIABLES
#include "a.h"
... // rest of stuff

or, alternatively, define this macro for a.cpp in the properties section of the file (Fileview pane->right click on a.cpp->Settings->Preprocessor definitions). Good luck. Let me know if I can give you more assistance. Joaquín M López Muñoz Telefónica, Investigación y Desarrollo