+/*
+ * Variables (and user-defined functions)
+ */
+static LIST_HEAD(variable_list);
+
+struct variable {
+ char *name;
+ char *value;
+ enum variable_flavor flavor;
+ int exp_count;
+ struct list_head node;
+};
+
+static struct variable *variable_lookup(const char *name)
+{
+ struct variable *v;
+
+ list_for_each_entry(v, &variable_list, node) {
+ if (!strcmp(name, v->name))
+ return v;
+ }
+
+ return NULL;
+}
+
+static char *variable_expand(const char *name, int argc, char *argv[])
+{
+ struct variable *v;
+ char *res;
+
+ v = variable_lookup(name);
+ if (!v)
+ return NULL;
+
+ if (argc == 0 && v->exp_count)
+ pperror("Recursive variable '%s' references itself (eventually)",
+ name);
+
+ if (v->exp_count > 1000)
+ pperror("Too deep recursive expansion");
+
+ v->exp_count++;
+
+ if (v->flavor == VAR_RECURSIVE)
+ res = expand_string_with_args(v->value, argc, argv);
+ else
+ res = xstrdup(v->value);
+
+ v->exp_count--;
+
+ return res;
+}
+
+void variable_add(const char *name, const char *value,
+ enum variable_flavor flavor)
+{
+ struct variable *v;
+ char *new_value;
+ bool append = false;
+
+ v = variable_lookup(name);
+ if (v) {
+ /* For defined variables, += inherits the existing flavor */
+ if (flavor == VAR_APPEND) {
+ flavor = v->flavor;
+ append = true;
+ } else {
+ free(v->value);
+ }
+ } else {
+ /* For undefined variables, += assumes the recursive flavor */
+ if (flavor == VAR_APPEND)
+ flavor = VAR_RECURSIVE;
+
+ v = xmalloc(sizeof(*v));
+ v->name = xstrdup(name);
+ v->exp_count = 0;
+ list_add_tail(&v->node, &variable_list);
+ }
+
+ v->flavor = flavor;
+
+ if (flavor == VAR_SIMPLE)
+ new_value = expand_string(value);
+ else
+ new_value = xstrdup(value);
+
+ if (append) {
+ v->value = xrealloc(v->value,
+ strlen(v->value) + strlen(new_value) + 2);
+ strcat(v->value, " ");
+ strcat(v->value, new_value);
+ free(new_value);
+ } else {
+ v->value = new_value;
+ }
+}
+
+static void variable_del(struct variable *v)
+{
+ list_del(&v->node);
+ free(v->name);
+ free(v->value);
+ free(v);
+}
+
+void variable_all_del(void)
+{
+ struct variable *v, *tmp;
+
+ list_for_each_entry_safe(v, tmp, &variable_list, node)
+ variable_del(v);
+}
+