problem in adding multiple source and header files to my code

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I am wirting a program in visual c++.I made one header file named as basic.h which contains global variables and functions,and its source file basic.cpp contains their definitions.I have made another header file matrixB.h and its source file matrixB.cpp.Main program and matrixB.cpp uses the global variables from basic.h.
when I try to compile my code I got the errors of redefinition and missing type specifier.If anyone knows please help me.
I have also uploaded my project at media fire.http://www.mediafire.com/?o8leol9q92v1d8x

thanks in advance

Ishtiaq

Posted 15-Mar-11 9:05am

smishtiaqhussain

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Albert Holguin 15-Mar-11 19:28pm

although the comments below answer the question... you should try to add code snippets here instead of linking to a compressed file on the net... can't speak for anyone but myself, but I'm not about to download and extract files from the internet from an unknown source...

2 solutions

Solution 2

In addition to what Niklas said, make sure your .h files are protected against multiple includes by using a header guard or #pragma once.

Posted 15-Mar-11 12:24pm

Hans Dietrich

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Albert Holguin 15-Mar-11 19:25pm

...or #ifndef guards...

Hans Dietrich 15-Mar-11 19:30pm

aka header guard. :)

Albert Holguin 15-Mar-11 19:34pm

my 5!

smishtiaqhussain 15-Mar-11 19:42pm

Thanks a lot for ur help and quick reply.....as you people suggested I have declared the global variables in header file with a keyword extern.and then I have define my these variables in cpp file.I have also added guard header to my header file using these command at start of header file

#ifndef BASIC_H
#define BASIC_H

and this at end of header file

#endif

.I have these commands in both header files.Now I am getting 6 errors of this kind.

Error   4   error LNK2001: unresolved external symbol "int oilvariables" (?oilvariables@@3HA)   basic.obj

I have also posted updated project at the link.http://www.mediafire.com/?whzjagw3waio9qi

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Niklas L · Accepted Answer · 2011-03-15T09:55:00

You should not declare global variables in a header file, unless you use the keyword extern and then define them in one cpp file. If you do, you might end up with multiple defined variables as you describe when two different cpp files are compiled and put the variables in their object code for linking. The linker will see the same variable twice.

You could get around this in a better way by putting your global variables as class members (declared static) in a class.