Compiling error when placing bool function in void loop (void) in IDE

1

Hi all

I am having a problem with compiling error when placing bool function in void loop (void) in atom IDE.

The error message is LD returned 1 exit status

this is function code in library source file not in the main source program
bool graphicMidline1(bool bInit)
{
// are we initializing?
if (bInit)
{
PRINTS("\n— Midline1 init");
resetMatrix();
bInit = false;
}
else
{
mx.drawLine(3, 0, 3, mx.getColumnCount()-1, true);
mx.drawLine(4, 0, 4, mx.getColumnCount()-1, true);
}

return(bInit);
}

Can any one help me with it

thanks