+/*
+ * Function parameters and return types have a few restrictions that are
+ * really easy to check in comparison to the above absurdity.
+ */
+static int
+check_parameters(struct cdecl_declarator **p, struct cdecl_declarator *d)
+{
+ struct cdecl_declspec *spec;
+ struct cdecl *param;
+ bool has_void = false;
+
+ if (d->type != CDECL_DECL_FUNCTION)
+ return 0;
+
+ for (param = d->u.function.parameters; param; param = param->next) {
+ if (!valid_declspecs(param, false))
+ return -1;
+
+ for (spec = param->specifiers; spec; spec = spec->next) {
+ if (spec->type == CDECL_TYPE_VOID
+ && param->declarators->type == CDECL_DECL_NULL)
+ has_void = true;
+ }
+ }
+
+ if (has_void && d->u.function.parameters->next) {
+ fprintf(stderr, "a void parameter must stand alone\n");
+ return -1;
+ } else if (has_void && d->u.function.variadic) {
+ fprintf(stderr, "variadic functions cannot have a void parameter\n");
+ return -1;
+ }
+
+ return 0;
+}
+
+/*
+ * Functions cannot return arrays or functions. Since the parse tree is
+ * "inside-out", we need to look for functions as the child declarator.
+ */
+static int
+check_rettypes(struct cdecl_declarator **p, struct cdecl_declarator *d)
+{
+ if (!d->child || d->child->type != CDECL_DECL_FUNCTION)
+ return 0;
+
+ switch (d->type) {
+ case CDECL_DECL_FUNCTION:
+ fprintf(stderr, "functions cannot return functions\n");
+ return -1;
+ case CDECL_DECL_ARRAY:
+ fprintf(stderr, "functions cannot return arrays\n");
+ return -1;
+ }
+
+ return 0;
+}
+
+static int
+check_arrays(struct cdecl_declarator **p, struct cdecl_declarator *d)
+{
+ if (!d->child || d->child->type != CDECL_DECL_ARRAY)
+ return 0;
+
+ switch (d->type) {
+ case CDECL_DECL_FUNCTION:
+ fprintf(stderr, "array members cannot be functions\n");
+ return -1;
+ }
+
+ return 0;
+}
+