Redifinition error

I have a cpp code that runs well in VS2010. When I try to run it on Matlab 2010a by using mex command, it gives redefinition error.

c:\users\amit\documents\matlab\real_c++\redacmodel.cpp(20) : error C2371: 'FORCE' : redefinition; different basic types 
c:\users\amit\documents\matlab\real_c++\blueacmodel.cpp(20) : see declaration of 'FORCE'

What is the reason? Thanks in advance.

Answer 1

[Walter Roberson]

I would speculate that FORCE is an "extern" variable in the two .cpp files.

The two .cpp files define FORCE with different data types. Look at line 20 of each of the two different source files to see how it is defined for the two.

[Amit Kalhapure]

Yes there are 2 different .cpp files, blueacmodel and redacmodel. At both places I have used same structure variable 'FORCE'.

typedef struct

{

double x;

double y;

}FORCE

[Walter Roberson]

That does not declare a structure variable: that declares a type alias named FORCE .

It appears you might be running into a problem with ISO C section 6.7.2.3 "Tags", paragraph 4:

Two declarations of structure, union, or enumerated types which are in different scopes or

use different tags declare distinct types. Each declaration of a structure, union, or

enumerated type which does not include a tag declares a distinct type.

The two FORCE are thus considered to be different types, and if a single scope saw both definitions then it would be an error, a redefinition of FORCE.

Please check whether one of those two files #include's the other: they probably should not.

[Walter Roberson]

You can find an unofficial copy of ISO C at http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1124.pdf

[Amit Kalhapure]

Thanks for your reply, I have found another solution for this problem

If I use following command then I'm able to get rid of redefinition error.

mex -v mesh.cpp blueacmodel.cpp redacmodel.cpp

mesh.cpp is the main source code here. but the new error I'm getting now is

LINK : error LNK2001: unresolved external symbol mexFunction

C:\USERS\AMIT\APPDATA\LOCAL\TEMP\MEX_3K~1\templib.x : fatal error LNK1120: 1 unresolved externals

C:\PROGRA~1\MATLAB\R2010A\BIN\MEX.PL: Error: Link of 'mesh.mexw32' failed.

What to do?

Thanks again.