Trying to debug include files

I did what you said, but i have a new problem
Several of my C files uses the same global variables declared on main, but the compiler tells me:

 Error 202: "var_name" undefined identifier 

I did what you said, but i have a new problem
Several of my C files uses the same global variables declared on main, but the compiler tells me:

 Error 202: "var_name" undefined identifier 

Javier,

At the top of all the files OTHER than main that use these variables, you must put an "extern" declaration to let the linker know where to find these variables. For instance, if you had an integer variable named "var1" in main.c that you wanted to use in foo.c, then somewhere at the top of foo.c you would put:

extern int var1

whoops... throw a ";" after the var1 in my last message.

Thanks a lot. I have done some C programming, but it's the first time i try to debug the include files....

Know i get an error
ERROR L104 : MULTIPLE PUBLIC DEFINITIONS

HOw do i solve this. I use the global variables in several c files besides main

Javier,

You need to DEFINE the variable in only ONE C file and DECLARE them as extern in the other files. For instance, if you define a global variable named "bar" in every C file you have and you want them all to refer to the same location in memory, then you'd put

unsigned char bar;

extern unsigned char bar;

At the top of all the files OTHER than main that use these variables, you must put an "extern" declaration

No. As I keep pointing out, pretty much every occurence of the word 'extern' in a .c file is a design error.

You should have this 'extern' in a header file instead, and #include that in exactly those source files that refer to it, including the one that holds the definition of the variable in question.

At the top of all the files OTHER than main that use these variables, you must put an "extern" declaration

No. As I keep pointing out, pretty much every occurence of the word 'extern' in a .c file is a design error.

You should have this 'extern' in a header file instead, and #include that in exactly those source files that refer to it, including the one that holds the definition of the variable in question.

Hans,

While I understand your philosophy, keep in mind that Javier started off this thread by asking how he could STEP THROUGH CODE included in a header file. I'm just going for simplicity here at the moment. He'll learn the theology of things the hard way at some later date, no doubt.

first time i try to debug the include files....

Just to make this extra clear: the problem is this that there's not supposed to be anything in an include file that would need to be debugged (in the sense that you need to search for errors in there although the compiler and linker already accepted the program).

You really need to brush up your basic knowledge of C. I suggest the comp.lang.c FAQ for starters, or possibly one of the textbooks recommended by that FAQ.

I had already done exactly what you said, but the problem isn't with the compiler, but with the linker
the full message is:

linking..
***ERROR L104: MULTIPLE PUBLIC DEFINITIONS
      SYMBOL: variable
      MODULE: Timer.obj(Timer) (this is my c file)

Javier,

You've missed something. The linker is complaining that there's more than one definition for "variable." This means that you have it in more than one C file without an extern tag in front of it. Another possibility is that there is a definition in one of the header files that you initially wanted to "debug." Either remove it from there, or put an extern tag in front of it if that's the case.

Jay,
the exact definition is
unsigned char tecla='N';
in the main C file
an the declarations are
extern unsigned char tecla='N';
in all other c files, and i still have the same problem.
The "include" files that i initially wanted to debug are now saved as .c files and included in the sourcegroup. This files have pure C code. I don't know what else should i do.
Thanks a lot

Javier,

This problem is again, one that has only to do with basic C programming. Anything that allocates space is a DEFINITION. This means that any place you have an "=" after a variable to initialize it is a definition. So... you need to have the line

unsigned char tecla='N';

extern unsigned char tecla;

Thanks a lot jay and you all, finally i made it. As hans said i used a header for the extern an th e declarations in the main. I also worked without the "=", but i don't kwon why because i had already tested that

"the problem isn't with the compiler, but with the linker"

NO.

The problem is with neither the compiler nor the linker - it is with your code.

The compiler only "sees" one 'C' source file at a time; each of your files is "correct" in itself, so you get no compiler errors.

The problem comes when you try to link the two separate object files together; only then can it be seen that you have two files both defining variables with the same name!

That's why the Linker tells you, "MULTIPLE PUBLIC DEFINITIONS" - because that's exactly what you've got!

What you want is just a single definition, and to have all the rest of your code refer to that one "global" variable.

If, on the other hand, you had wanted two distinct, independent global variables - then you would have had to rename at least one of them.