Create bcheck region for argv and arge argument

For program manipulating argv or arge as pointer with construct such as:

(while *argv++) {
  do_something_with_argv;
}

it is necessary to have argv and arge inside a region. This patch create
regions argv and arge) if main is declared with those parameters.

lib/bcheck.c

@@ -418,6 +418,13 @@ void __bound_init(void)
     }
 }
 
+void __bound_main_arg(void **p)
+{
+    void *start = p;
+    while (*p++);
+    __bound_new_region(start, (void *) p - start);
+}
+
 void __bound_exit(void)
 {
     restore_malloc_hooks();

tccgen.c

@@ -5770,6 +5770,21 @@ static void gen_function(Sym *sym)
     /* push a dummy symbol to enable local sym storage */
     sym_push2(&local_stack, SYM_FIELD, 0, 0);
     gfunc_prolog(&sym->type);
+#ifdef CONFIG_TCC_BCHECK
+    if (tcc_state->do_bound_check
+        && !strcmp(get_tok_str(sym->v, NULL), "main")) {
+        int i;
+
+        sym = local_stack;
+        for (i = 0, sym = local_stack; i < 2; i++, sym = sym->prev) {
+            if (sym->v & SYM_FIELD || sym->prev->v & SYM_FIELD)
+                break;
+            vpush_global_sym(&func_old_type, TOK___bound_main_arg);
+            vset(&sym->type, sym->r, sym->c);
+            gfunc_call(1);
+        }
+    }
+#endif
     rsym = 0;
     block(NULL, NULL, NULL, NULL, 0, 0);
     gsym(rsym);

tcctok.h

@@ -237,6 +237,7 @@
      DEF(TOK___bound_ptr_indir8, "__bound_ptr_indir8")
      DEF(TOK___bound_ptr_indir12, "__bound_ptr_indir12")
      DEF(TOK___bound_ptr_indir16, "__bound_ptr_indir16")
+     DEF(TOK___bound_main_arg, "__bound_main_arg")
      DEF(TOK___bound_local_new, "__bound_local_new")
      DEF(TOK___bound_local_delete, "__bound_local_delete")
 # ifdef TCC_TARGET_PE