Fix build warning - cast from pointer to integer of different size

object->values used to be a size in pass 1 and a pointer in pass 2. A union has been added to avoid such GCC warning: * cast from pointer to integer of different size * dereferencing type-punned pointer will break strict-aliasing rules The union is visible only when JSON__PRVATE_API is defined, but this trick relies on sizeof(json_object_entry *) >= sizeof(unsigned int). Is that acceptable? The name of the new union is "_p" (as in private) instead of "u", but it could be renamed back to "u", or even "_reserved" or "_r".
json-parser · Aug 28, 2021 · a04c7c6 · a04c7c6
1 parent 60fd8a7
commit a04c7c6
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Showing 2 changed files with 39 additions and 12 deletions.
diff --git a/json.c b/json.c
@@ -27,6 +27,7 @@
  * SUCH DAMAGE.
  */
 
+#define JSON__PRIVATE_API
 #include "json.h"
 
 #ifdef _MSC_VER
@@ -151,15 +152,15 @@ static int new_value (json_state * state,
             if (value->u.object.length == 0)
                break;
 
-            values_size = sizeof (*value->u.object.values) * value->u.object.length;
+            values_size = sizeof (*value->u.object._p.values) * value->u.object.length;
 
-            if (! (value->u.object.values = (json_object_entry *) json_alloc
-                  (state, values_size + ((unsigned long) value->u.object.values), 0)) )
+            if (! (value->u.object._p.values = (json_object_entry *) json_alloc
+                  (state, values_size + value->u.object._p._reserved_length, 0)) )
             {
                return 0;
             }
 
-            value->_reserved.object_mem = (*(char **) &value->u.object.values) + values_size;
+            value->_reserved.object_mem = (*(char **) &value->u.object._p.values) + values_size;
 
             value->u.object.length = 0;
             break;
@@ -422,13 +423,13 @@ json_value * json_parse_ex (json_settings * settings,
                   case json_object:
 
                      if (state.first_pass)
-                        (*(json_char **) &top->u.object.values) += string_length + 1;
+                        top->u.object._p._reserved_length += string_length + 1;
                      else
                      {
-                        top->u.object.values [top->u.object.length].name
+                        top->u.object._p.values [top->u.object.length].name
                            = (json_char *) top->_reserved.object_mem;
 
-                        top->u.object.values [top->u.object.length].name_length
+                        top->u.object._p.values [top->u.object.length].name_length
                            = string_length;
 
                         (*(json_char **) &top->_reserved.object_mem) += string_length + 1;
@@ -905,7 +906,7 @@ json_value * json_parse_ex (json_settings * settings,
                {
                   case json_object:
 
-                     parent->u.object.values
+                     parent->u.object._p.values
                         [parent->u.object.length].value = top;
 
                      break;
@@ -1011,11 +1012,11 @@ void json_value_free_ex (json_settings * settings, json_value * value)
 
             if (!value->u.object.length)
             {
-               settings->mem_free (value->u.object.values, settings->user_data);
+               settings->mem_free (value->u.object._p.values, settings->user_data);
                break;
             }
 
-            value = value->u.object.values [-- value->u.object.length].value;
+            value = value->u.object._p.values [-- value->u.object.length].value;
             continue;
 
          case json_string:

diff --git a/json.h b/json.h
@@ -121,14 +121,35 @@ typedef struct _json_value
       {
          unsigned int length;
 
+#ifdef JSON__PRIVATE_API
+         union
+         {
+            json_object_entry * values;
+            unsigned int _reserved_length;
+
+         } _p;
+#else
          json_object_entry * values;
+#endif
 
          #if defined(__cplusplus)
          json_object_entry * begin () const
-         {  return values;
+         {
+#ifdef JSON__PRIVATE_API
+            return _p.values;
+#else
+            return values;
+#endif
+
          }
          json_object_entry * end () const
-         {  return values + length;
+         {
+#ifdef JSON__PRIVATE_API
+            return _p.values + length;
+#else
+            return values + length;
+#endif
+
          }
          #endif
 
@@ -195,8 +216,13 @@ typedef struct _json_value
                return json_value_none;
 
             for (unsigned int i = 0; i < u.object.length; ++ i)
+#ifdef JSON__PRIVATE_API
+               if (!strcmp (u.object._p.values [i].name, index))
+                  return *u.object._p.values [i].value;
+#else
                if (!strcmp (u.object.values [i].name, index))
                   return *u.object.values [i].value;
+#endif
 
             return json_value_none;
          }