I try to convert C Code from Standard 11 to 14. I work with gcc 7.5.0 in Ubuntu 20.04. I have the following lines of code
json.h:
extern const struct _json_value json_value_none;typedef struct _json_object_entry{ json_char * name; unsigned int name_length; struct _json_value * value;} json_object_entry;typedef struct _json_value{ struct _json_value * parent; json_type type; union { int boolean; json_int_t integer; double dbl; struct { unsigned int length; json_object_entry * values; } object; } u; union { struct _json_value * next_alloc; void * object_mem; } _reserved;} json_value;json.c
static int new_value (json_state * state, json_value ** top, json_value ** root, json_value ** alloc, json_type type){ json_value * value; int values_size; if (!state->first_pass) { value = *top = *alloc; *alloc = (*alloc)->_reserved.next_alloc; if (!*root) *root = value; switch (value->type) { case json_array: ... break; case json_object: if (value->u.object.length == 0) break; values_size = sizeof (*value->u.object.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)) ) { return 0; } value->_reserved.object_mem = (*(char **) &value->u.object.values) + values_size; ... break; }; return 1; } ... return 1;}When I compile, I got dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]for the following line
value->_reserved.object_mem = (*(char **) &value->u.object.values) + values_sizeI googled and found this link who means that the problem is probably because object_mem is defined with a void *type, who is an undefined type. I tried to substitute it by int * type, without success. I'm stucked.
Any helps are welcome.