Introduce refcounted simple values

When storing object location, the singleton true, false and null objects are problematic since they are indistinguishable from each other. Overcome this by introducing a refcounted variant to allocate when JSON_STORE_LOCATION flag was given. Signed-off-by: Phil Sutter <[email protected]>
akheron · Sep 28, 2023 · 9535972 · 9535972
1 parent 15218cc
commit 9535972
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Showing 4 changed files with 73 additions and 5 deletions.
diff --git a/src/jansson_private.h b/src/jansson_private.h
@@ -60,11 +60,16 @@ typedef struct {
     json_int_t value;
 } json_integer_t;
 
+typedef struct {
+    json_t json;
+} json_simple_t;
+
 #define json_to_object(json_)  container_of(json_, json_object_t, json)
 #define json_to_array(json_)   container_of(json_, json_array_t, json)
 #define json_to_string(json_)  container_of(json_, json_string_t, json)
 #define json_to_real(json_)    container_of(json_, json_real_t, json)
 #define json_to_integer(json_) container_of(json_, json_integer_t, json)
+#define json_to_simple(json_)  container_of(json_, json_simple_t, json)
 
 /* Create a string by taking ownership of an existing buffer */
 json_t *jsonp_stringn_nocheck_own(const char *value, size_t len);
@@ -94,6 +99,9 @@ char *jsonp_strndup(const char *str, size_t len) JANSSON_ATTRS((warn_unused_resu
 int jsonp_loop_check(hashtable_t *parents, const json_t *json, char *key, size_t key_size,
                      size_t *key_len_out);
 
+/* Helpers for location information */
+json_t *jsonp_simple(json_t *json, size_t flags);
+
 /* Windows compatibility */
 #if defined(_WIN32) || defined(WIN32)
 #if defined(_MSC_VER) /* MS compiller */

diff --git a/src/load.c b/src/load.c
@@ -812,15 +812,15 @@ static json_t *parse_value(lex_t *lex, size_t flags, json_error_t *error) {
         }
 
         case TOKEN_TRUE:
-            json = json_true();
+            json = jsonp_simple(json_true(), flags);
             break;
 
         case TOKEN_FALSE:
-            json = json_false();
+            json = jsonp_simple(json_false(), flags);
             break;
 
         case TOKEN_NULL:
-            json = json_null();
+            json = jsonp_simple(json_null(), flags);
             break;
 
         case '{':

diff --git a/src/value.c b/src/value.c
@@ -997,6 +997,33 @@ json_t *json_null(void) {
     return &the_null;
 }
 
+/*** refcounted simple values ***/
+
+json_t *jsonp_simple(json_t *json, size_t flags)
+{
+    json_simple_t *simple;
+
+    /* pointless if not recording object location */
+    if (!(flags & JSON_STORE_LOCATION))
+        return json;
+
+    simple = jsonp_malloc(sizeof(json_simple_t));
+    if (!simple)
+        return NULL;
+
+    simple->json.type = json->type;
+    simple->json.refcount = 1;
+
+    return &simple->json;
+}
+
+static void json_delete_simple(json_simple_t *simple)
+{
+    /* catch accidental calls for singletons */
+    if (simple && simple->json.refcount == 0)
+        jsonp_free(simple);
+}
+
 /*** deletion ***/
 
 void json_delete(json_t *json) {
@@ -1019,11 +1046,14 @@ void json_delete(json_t *json) {
         case JSON_REAL:
             json_delete_real(json_to_real(json));
             break;
+        case JSON_TRUE:
+        case JSON_FALSE:
+        case JSON_NULL:
+            json_delete_simple(json_to_simple(json));
+            break;
         default:
             return;
     }
-
-    /* json_delete is not called for true, false or null */
 }
 
 /*** equality ***/

diff --git a/test/suites/api/test_load.c b/test/suites/api/test_load.c
@@ -224,6 +224,35 @@ static void error_code() {
         fail("json_loads returned incorrect error code");
 }
 
+static void singleton_or_not() {
+    const char *simple_types[] = { "true", "false", "null", NULL };
+    size_t flags;
+    json_t *json;
+    int i;
+
+    for (i = 0; simple_types[i]; i++) {
+        flags = JSON_DECODE_ANY;
+        json = json_loads(simple_types[i], flags, NULL);
+        if (!json)
+            fail_args("json_loads failed for %s", simple_types[i]);
+        if (json->refcount != (size_t)-1)
+            fail_args("expected singleton when loading %s", simple_types[i]);
+        json_delete(json);
+
+        flags |= JSON_STORE_LOCATION;
+        json = json_loads(simple_types[i], flags, NULL);
+        if (!json)
+            fail_args("json_loads failed for %s when storing location",
+                      simple_types[i]);
+        if (json->refcount != 1)
+            fail_args("unexpected singleton when loading %s and storing location",
+                      simple_types[i]);
+        json_delete(json);
+        json_decref(json);
+    }
+}
+
+
 static void run_tests() {
     file_not_found();
     very_long_file_name();
@@ -235,4 +264,5 @@ static void run_tests() {
     load_wrong_args();
     position();
     error_code();
+    singleton_or_not();
 }