apply const qualifier appropriately

src/frontend/arg.c

@@ -78,10 +78,12 @@ arg_plot(const wordlist *wl, const struct comm *command)
 
 
 void
-arg_load(wordlist *wl, const struct comm *command)
+arg_load(const wordlist *wl_in, const struct comm *command)
 {
     /* just call com_load */
+    wordlist* const wl = wl_copy(wl_in);
     command->co_func(wl);
+    wl_free(wl);
 }
 
 

src/frontend/arg.h

@@ -10,7 +10,7 @@ char *prompt(FILE *fp);
 wordlist *process(wordlist *wlist);
 void arg_print(const wordlist *wl, const struct comm *command);
 void arg_plot(const wordlist *wl, const struct comm *command);
-void arg_load(wordlist *wl, const struct comm *command);
+void arg_load(const wordlist *wl, const struct comm *command);
 void arg_let(const wordlist *wl, const struct comm *command);
 void arg_set(const wordlist *wl, const struct comm *command);
 void arg_display(const wordlist *wl, const struct comm *command);

src/include/ngspice/cpdefs.h

@@ -41,7 +41,7 @@ struct comm {
     int co_maxargs;
 
     /* The fn that prompts the user. */
-    void (*co_argfn) (wordlist *wl, struct comm *command);
+    void (*co_argfn) (const wordlist *wl, const struct comm *command);
 
     /* When these are printed, printf(string, av[0]) .. */
     char *co_help;