+
+ new = reduce_function(d->u.function.parameters);
+ if (!new)
+ return 0; /* e.g. int (foo bar) */
+ *p = new;
+ free(d->child);
+ free(d);
+
+ return 1;
+}
+
+/*
+ * The parser's bias towards considering things as functions whenever possible
+ * makes nested parentheses tricky. (x) is considered to be part of a function
+ * declarator until simplify_functions converts it. The problem is that
+ * (((x))) is not valid as part of a function declarator, but it *is* valid
+ * as an identifier enclosed 3 times in parentheses. This is complicated by
+ * the fact that things like (((int))) are not valid anywhere.
+ *
+ * To avoid ambiguities, the parser actually emits a "function" declarator for
+ * every pair of parentheses. The ones that can't reasonably be functions
+ * consist of a single "parameter" with no declaration specifiers (note that
+ * every valid function parameter will have at least one type specifier).
+ *
+ * This pass is to remove these fake functions from the parse tree. We take
+ * care to avoid turning invalid things like ((int)) into valid things like
+ * (int) by observing that the only valid function declarators that appear
+ * in these "fake" parentheses are those that have a non-null child declarator
+ * (for instance, int ((*)(int)) *or* those that will be eliminated by the
+ * simplify_functions pass.
+ */
+
+static int
+reduce_parentheses(struct cdecl_declarator **p, struct cdecl_declarator *d)
+{
+ struct cdecl *param;
+
+ if (d->type != CDECL_DECL_FUNCTION)
+ return 0;
+
+ param = d->u.function.parameters;
+ if (param && param->specifiers == NULL) {
+ struct cdecl_declarator *decl;
+
+ assert(!param->next);
+
+ decl = param->declarators;
+ if (decl->type == CDECL_DECL_NULL) {
+ free(decl);
+ free(param);
+ d->u.function.parameters = NULL;
+ return 0;
+ }
+
+ if (d->child->type != CDECL_DECL_NULL) {
+ fprintf(stderr, "invalid function parameter\n");
+ return -1;
+ }
+
+ free(d->child);
+ free(param);
+ free(d);
+ *p = decl;
+
+ /*
+ * We may have replaced d with another fake function which
+ * also needs to be eliminated.
+ */
+ if (reduce_parentheses(p, decl) < 0)
+ return -1;
+
+ /*
+ * If the remaining declarator is a function, make sure it's
+ * valid by checking its reducibility.
+ */
+ decl = *p;
+ if (decl->type == CDECL_DECL_FUNCTION
+ && decl->child->type == CDECL_DECL_NULL
+ && !function_is_reducible(decl)) {
+ fprintf(stderr, "too many parentheses in function\n");
+ return -1;
+ }
+
+ return 1;