(Also seen on MudBytes.net)

So, in trying to add a new global variable to keep track of the last color used by the MUD, but I've run into a bit of an issue. The code itself compiles, up until the very end when I receive this error message:

$make -s smaug
  Compiling o/color.o....
o/color.o: In function `_Z11set_lastcolPc':
.../quarulid/src/color.c:1878: undefined reference to `_last_col'
.../quarulid/src/color.c:1884: undefined reference to `_last_col'
collect2: ld returned 1 exit status
make[1]: *** [smaug] Error 1
make: *** [all] Error 2

However, in mud.h I certainly have this:

extern char last_col[2];

The code the uses last_col is:

void set_lastcol( char *col )
{
	char thecol[2] ;

	if( !col && !IS_NULLSTR(col))
	{
		thecol[0] = 'x' ;
		thecol[1] = '\0' ;
		mudstrlcpy( last_col , thecol, 2 ) ;
		return ;
	}

	thecol[0] = col[0] ;
	thecol[1] = '\0' ;
	mudstrlcpy( last_col , thecol, 2 ) ;

	return ;
}

Not surprisingly, the error was exactly what the compiler had said.

Tyche said:

All I see is a declaration of last_col.
You don't define last_col anywhere in your program.

Maybe this page will help: TutorialFunctionDeclarationsAndDefinitions

What "extern char last_col[2];" means to the compiler is that there exists a variable called last_col somewhere.
It doesn't define it.

Bobo the bee said:

And, yep, this was indeed the problem. Not being used to larger-scale programs, I keep forgetting that setting something in a header file doesn't mean it exists as of yet. A simple error, and thanks for pointing it out. To any who might wonder, a declaration of

char last_col[2] ;

before set_lastcol() was the issue