Function defined in header not available in main file

Projects Programming
1

I have a file structure as follows:

interface.h --> interface.c
      |
      |
effects.h --> effects.c
      |
      |
    main

However, functions declared in effects.h are not accessible in main.

Code snippets :

main :

#include "interface.h"
#include "effects.h"
void setup()  //Initialize all variables here
{

....
turnoff();
};

effects.h :

#ifndef EFFECTS
#define EFFECTS
void turnoff();
#endif

effects.c :

#include "interface.h"
#include "effects.h"
void turnoff()
{
....
};

interface.h :

#ifndef INTERFACE
#define INTERFACE
....
#endif

Error message : In function loop':undefined reference to turnoff()'

Anybody knows whats wrong ?

2

Anybody knows whats wrong ?

I c what the problem is. Changing to cpp would help.

3

Why ? Doesnt avr-gcc handle c ??

http://arduino.cc/en/Hacking/BuildProcess

4

Yes, it does. However, C++ supports function overloading. That is the same function can be called with different arguments. How do you suppose the compiler knows which code to actually execute when you type Serial.print(val);?

The answer is that every function really gets a different name. That name is made up of the function name and the types of the arguments that the function accepts.

So, Serial.print() for an int is a different name what Serial.print() for a float.

The C++ compiler is looking for a function based on the name and the arguments that the function accepts.

The C compiler, because it does not support function overloading, knows that the function name is unique, so it doesn't mangle the name.

The linker, then, can't find the mangled name it is looking for in the object file produced by the C compiler.

5

I changed the files to .cpp and it worked. What I still dont understand is why ? If my project is completely in C or C++ then the linker should be able to handle it. What you describe should cause problems when i mix C and C++ together, if I understood you correctly.

6

What I still dont understand is why ?

I described why. You could google "C++ name mangling" for more details.

If my project is completely in C or C++ then the linker should be able to handle it.

And it can. The IDE creates a cpp file from the sketch, though.

What you describe should cause problems when i mix C and C++ together, if I understood you correctly.

Well? Didn't it?