Visual Studio Linker problems

[BryanColorado]

All,

Happy New Year to all my fellow developers. The holidays are a great time to write code with everyone taking time off, it is really quiet and allows for many uninterrupted hours.

My question is hopefully pretty simple. I wrote a routine in one C++ file and I decided to break it up into some smaller more manageable C++ files. When I copied the variables out of the first one and into the new smaller file (same solution), everything compiles fine but I get a ton of linker errors saying the variables have already been defined in another (the previous) file.

Using Visual Studio 2008. Suggestions?

Thanks,
Bryan

[ljs]

i´m not sure i understood what you are trying to do. do you want to spread a single function over several cpp or h files? as far as i know that is not common practice.

[pogrady]

you need to use the extern keyword when defining global variables.

extern [type] [identifier]

header file

//....
extern int gSolution;

implementation file

int gSolution = 10;

this tells the compiler that there is an integer variable somehwere and to look for it when linking.

[BryanColorado]

Thanks for the responses, let me clarify. These are not global variables. I am simply making two separate routines (c++ files) from one to make the code less cumbersome and more modular. In making two routines, I have to take some variables out of the original and move them to the new one.

It would be as if you had a program, say program X that had 4 variables in it where two of the variables did one thing like B=A+4 and D=C+5. Now I want to make another program (Y) and take C & D out of X and put them into Y. Compiles fine but linker says C & D already defined in program X. Of course I'm dealing with a lot more variables resulting in a lot of the same linker errors. See below.

Thanks much.
Bryan

>PageComputeGeoInverse.obj : error LNK2005: "double EllipsoidSemiMinor" (?EllipsoidSemiMinor@@3NA) already defined in Frontier Geodetic.obj
5>PageComputeGeoInverse.obj : error LNK2005: "double EllipsoidAverage" (?EllipsoidAverage@@3NA) already defined in Frontier Geodetic.obj
5>PageComputeGeoInverse.obj : error LNK2005: "double FlateningInverse" (?FlateningInverse@@3NA) already defined in Frontier Geodetic.obj
5>PageComputeGeoInverse.obj : error LNK2005: "double EllipsoidSemiMajor" (?EllipsoidSemiMajor@@3NA) already defined in Frontier Geodetic.obj
5>PageComputeGeoInverse.obj : error LNK2005: "double Flatening" (?Flatening@@3NA) already defined in Frontier Geodetic.obj
5>UITask_ComputeGeoInverse.obj : error LNK2005: "double EllipsoidSemiMinor" (?EllipsoidSemiMinor@@3NA) already defined in Frontier Geodetic.obj
5>UITask_ComputeGeoInverse.obj : error LNK2005: "double EllipsoidAverage" (?EllipsoidAverage@@3NA) already defined in Frontier Geodetic.obj
5>UITask_ComputeGeoInverse.obj : error LNK2005: "double FlateningInverse" (?FlateningInverse@@3NA) already defined in Frontier Geodetic.obj
5>UITask_ComputeGeoInverse.obj : error LNK2005: "double EllipsoidSemiMajor" (?EllipsoidSemiMajor@@3NA) already defined in Frontier Geodetic.obj
5>UITask_ComputeGeoInverse.obj : error LNK2005: "double Flatening" (?Flatening@@3NA) already defined in Frontier Geodetic.obj
5>UITask_GeoInverse.obj : error LNK2005: "double EllipsoidSemiMinor" (?EllipsoidSemiMinor@@3NA) already defined in Frontier Geodetic.obj
5>UITask_GeoInverse.obj : error LNK2005: "double EllipsoidAverage" (?EllipsoidAverage@@3NA) already defined in Frontier Geodetic.obj
5>UITask_GeoInverse.obj : error LNK2005: "double FlateningInverse" (?FlateningInverse@@3NA) already defined in Frontier Geodetic.obj
5>UITask_GeoInverse.obj : error LNK2005: "double EllipsoidSemiMajor" (?EllipsoidSemiMajor@@3NA) already defined in Frontier Geodetic.obj
5>UITask_GeoInverse.obj : error LNK2005: "double Flatening" (?Flatening@@3NA) already defined in Frontier Geodetic.obj
5>CalcGeoInverse.obj : error LNK2005: "double EllipsoidSemiMinor" (?EllipsoidSemiMinor@@3NA) already defined in Frontier Geodetic.obj
5>CalcGeoInverse.obj : error LNK2005: "double EllipsoidAverage" (?EllipsoidAverage@@3NA) already defined in Frontier Geodetic.obj
5>CalcGeoInverse.obj : error LNK2005: "double FlateningInverse" (?FlateningInverse@@3NA) already defined in Frontier Geodetic.obj
5>CalcGeoInverse.obj : error LNK2005: "double EllipsoidSemiMajor" (?EllipsoidSemiMajor@@3NA) already defined in Frontier Geodetic.obj
5>CalcGeoInverse.obj : error LNK2005: "double Flatening" (?Flatening@@3NA) already defined in Frontier Geodetic.obj
5> Creating library c:\Users\Bryan\Documents\Visual Studio 2008\Projects\Frontier Geodetic\Frontier Geodetic\Win32\Debug\Frontier Geodetic.lib and object c:\Users\Bryan\Documents\Visual Studio 2008\Projects\Frontier Geodetic\Frontier Geodetic\Win32\Debug\Frontier Geodetic.exp
5>c:\Users\Bryan\Documents\Visual Studio 2008\Projects\Frontier Geodetic\Frontier Geodetic\Win32\Debug\Frontier Geodetic.dll : fatal error LNK1169: one or more multiply defined symbols found
5>Build log was saved at "file://c:\Users\Bryan\Documents\Visual Studio 2008\Projects\Frontier Geodetic\Frontier Geodetic\Win32\Debug\BuildLog.htm"
5>Frontier Geodetic - 21 error(s), 0 warning(s)
=

[ljs]

but you are passing the variables as function parameters then? like in

--------file 1--------------

void somefunction(int& a)
{

}

---------------file 2----------------
extern void somefunction(int& a)

void otherfunction(int &b)
{
int pepe = 5;
somefunction(pepe);
}


anyway, what pogrady said also goes for functions in separate files- you must use the extern keyword to define in file A the functions that are used in file A but that are not there, for example

extern void somefunction(int& someparameter);

[jlb]

Please post your actual code, so we don't have to guess about your problem.

You should not need to add the extern keyword to your function prototypes.