Function declared in header not accessible in main file

Question

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()'

The error message doesnt make sense as loop function is empty !

@cnicutar I am using the Arduino IDE. Not compiling or linking manually. — asheeshr
– asheeshr, Commented Feb 10, 2013 at 14:59
It's likely you've not configured it correctly to link both files. — cnicutar
– cnicutar, Commented Feb 10, 2013 at 15:00
If you copied everything correctly... isn't one of your files in C++? (like, *.cxx or *.cpp rather than *.c?) — Anton Kovalenko
– Anton Kovalenko, Commented Feb 10, 2013 at 15:02
@AntonKovalenko No. Why ? The IDE should handle C code correctly. — asheeshr
– asheeshr, Commented Feb 10, 2013 at 15:04

Alexey Frunze · Accepted Answer · 2013-02-10 15:03:55Z

1

You need to compile and link all 3 .c files together. With gcc it's as simple as

gcc main.c interface.c effects.c -o executable_name

answered Feb 10, 2013 at 15:03

Alexey Frunze

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2 Comments

Alexey Frunze Over a year ago

That's not very relevant. You need to find out how to include all 3 .c files into the project in your IDE or whatever it is, so it invokes the compiler and linker with proper parameters.

asheeshr Over a year ago

The IDE abstracts away a lot of the stuff. The Arduino build process links the code to quite a few of its libraries and also specifies many parameters. At the moment, I really cant get into that.

Udo Klein · Accepted Answer · 2014-04-28 08:39:54Z

1

I think the IDE wants *.cpp files instead of *.c files.

Anyway you should change the settings under file->preferences to get verbose compiler output. Usually this gives some hints. At least it shows you the temporary directory that contains the files that are actually compiled. This in turn allows much more precise analysis of the issue.

edited Apr 28, 2014 at 8:39

answered Feb 10, 2013 at 19:08

Udo Klein

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1 Comment

kolosy Over a year ago

i had the same thing happen in arduino. renaming the .c to .cpp fixed it.

Ganesh · Accepted Answer · 2013-02-10 15:25:23Z

0

From the latest response, I feel that effects.c is not part of the compilation. I am not aware of the development environment, but from the available data, this is my observation.

answered Feb 10, 2013 at 15:25

Ganesh

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Comments

jpmuc · Accepted Answer · 2013-02-10 16:07:45Z

0

what are the flags you are using? maybe you need to declare your functions as extern explicitly?

extern void turnoff();

answered Feb 10, 2013 at 16:07

jpmuc

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