Source:
https://sources.debian.net/src/gtklp/1.3.1-0.1/debian/patches/bugs/644113.diff/

--- gtklp.orig/libgtklp/libgtklp.c
+++ gtklp/libgtklp/libgtklp.c
@@ -554,7 +554,7 @@ void passwin_response_ok(GtkEditable *ed
 
 const char *getPass (const char *prompt)
 {
-  GtkWidget *vbox, *hbox, *hbox1, *vbox1, *vbox2, *labell, *labelp, *yes, *no;
+  GtkWidget *vbox, *hbox, *vbox1, *vbox2, *labell, *labelp;
 	gint gi1;
 #if GTK_MAJOR_VERSION == 1
 	GtkWidget *sep,*passwin;
@@ -780,9 +780,6 @@ void exitOnError(char *gerror1, char *ge
 	GtkWidget *exitErrorDialog;
 	GtkWidget *hbox,*label,*pixmapwid;
 	char tmplabel[MAXLINE+1];
-	GtkStyle *style;
-	GdkPixmap *pixmap;
-	GdkBitmap *mask;
 #if GTK_MAJOR_VERSION == 1
 	GtkWidget *button,*vbox,*sep,*bbox;
 #endif
@@ -826,9 +823,9 @@ void exitOnError(char *gerror1, char *ge
 		gtk_widget_show(pixmapwid);
 
 		if(strlen(gerror2) == 0)
-			snprintf(tmplabel,(size_t)MAXLINE,gerror1);
+			snprintf(tmplabel,(size_t)MAXLINE,"%s",gerror1);
 		else
-			snprintf(tmplabel,(size_t)MAXLINE,gerror1,gerror2);
+			snprintf(tmplabel,(size_t)MAXLINE,"%s\n%s",gerror1,gerror2);
 		label=gtk_label_new(tmplabel);
 		gtk_box_pack_end(GTK_BOX(hbox),label,FALSE, FALSE,FRAME_SPACING_V);
 		gtk_widget_show(label);
@@ -856,7 +853,7 @@ void exitOnError(char *gerror1, char *ge
 #endif
 	} else {
 		if(strlen(gerror2) == 0)
-			g_warning(gerror1);
+			g_warning("%s",gerror1);
 		else
 			g_warning(gerror1,gerror2);
 	}
--- gtklp.orig/gtklp/gtklp.c
+++ gtklp/gtklp/gtklp.c
@@ -302,7 +302,7 @@ int main(int argc,char *argv[])
 			case '?':
 				if(calledGtkLP)
 				{
-					g_print(str2str(_("Usage: gtklp [-P|-d printer] [-c configdir] [-S server] [-U user] [-p port] [-l] [-D] [-V] [-b] [-i] [-# n] [-C] [-H] [-E] [-J jobname] [-q priority] [-o option=value ...] [file(s)]\n")));
+					g_print("%s", str2str(_("Usage: gtklp [-P|-d printer] [-c configdir] [-S server] [-U user] [-p port] [-l] [-D] [-V] [-b] [-i] [-# n] [-C] [-H] [-E] [-J jobname] [-q priority] [-o option=value ...] [file(s)]\n")));
 				}
 				return(0);
 			break;