Problem in file including.

Hi
I have problem in including file in a class. I have a fuction declared in .h file and define in .c file when i am trying to call it in my .cpp file then it gives error

error: undefined reference to `packet_formation(unsigned char, unsigned char)'
while i am including its header file.
But when by mistake i include its .c file then it is running accurately.
What is the problem i am not understanding, can we include .c(source file) , is it not unlogical including a source file while the header file has the declaration of function.

Please help me to understand this.

Is this function declared as extern in header ?
Is the .c file with function definition compiled and .o linked ?

no it is not declared with "extern".

Ok, if I remember correctly "extern" is not required for functions (only for variables existing in another file), so forget about it.
What about my second question ?

ya .c file compiled succesfully.

Can you show some relevant code ?
Simple code using function defined in .c file in .cpp file:

Code:

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// cfunc.h
#ifndef _FUNC_H_
#define _FUNC_H_
 
void func();
 
#endif

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Code:

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// cfunc.c
#include <stdio.h>
#include "cfunc.h"
 
void func(){
	printf("works?\n");
}

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Code:

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// main.cpp
extern "C"{
#include "cfunc.h"
}
 
int main(){
	func();
	return 0;
}

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Compile & run:

Quote:

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gcc -c cfunc.c
g++ main.cpp cfunc.o -o main.exe
main.exe // prints works ?

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