destroy `const' plot in com_quit()

src/frontend/misccoms.c

@@ -79,6 +79,7 @@ com_quit(wordlist *wl)
     destroy_ivars();
 
     byemesg();
+    destroy_const_plot();
     exit(exitcode);
 }
 

src/frontend/postcoms.c

@@ -22,6 +22,7 @@ Author: 1985 Wayne A. Christopher, U. C. Berkeley CAD Group
 #include "quote.h"
 #include "variable.h"
 #include "parser/complete.h" /* va: throwaway */
+#include "plotting/plotting.h"
 
 
 static void killplot(struct plot *pl);
@@ -856,6 +857,29 @@ killplot(struct plot *pl)
 }
 
 
+void
+destroy_const_plot(void)
+{
+    struct dvec *v, *nv = NULL;
+    struct plot *pl = &constantplot;
+
+    /*  pl_dvecs, pl_scale */
+    for (v = pl->pl_dvecs; v; v = nv) {
+        nv = v->v_next;
+        vec_free(v);
+    }
+    wl_free(pl->pl_commands);
+    if (pl->pl_ccom)    /* va: also tfree (memory leak) */
+        throwaway(pl->pl_ccom);
+
+    if (pl->pl_env) { /* The 'environment' for this plot. */
+        /* va: HOW to do? */
+        printf("va: killplot should tfree pl->pl_env=(%p)\n", pl->pl_env);
+        fflush(stdout);
+    }
+}
+
+
 /* delete all windows with graphs dedrived from a given plot */
 static void
 DelPlotWindows(struct plot *pl)

src/frontend/postcoms.h

@@ -16,5 +16,7 @@ void com_cross(wordlist *wl);
 void com_destroy(wordlist *wl);
 void com_splot(wordlist *wl);
 
+void destroy_const_plot(void);
+
 
 #endif