Memory Leak Using JSON-C

Question

I am new to JSON-C, Please see my sample code and let me know of it will create any memory leak, if yes then how to free JSON-C object.

    struct json_object *new_obj         = NULL;
    new_obj = json_tokener_parse(strRawJSON);
    new_obj = json_object_object_get(new_obj, "FUU");
    if(NULL == new_obj){
        SYS_OUT("\nFUU not found in JSON");
        return NO;
    }
    new_obj = json_object_object_get(new_obj, "FOO"); // I m re-using new_obj, without free it?  
    if(NULL == new_obj){
        SYS_OUT("\nFOO not found in JSON");
        return NO;
    }
    // DO I need to clean new_obj, if yes then how ??

Do I need to clean new_obj, if yes then how. Can some one help to understand how to do memory management JSON-C.

Thanks in Advance

A quick web search seems to indicate that JSON-C uses reference counting to manage `json_object` instances and the function used to "free" the instances is [json_object_put](http://oss.metaparadigm.com/json-c/doc/html/json__object_8h.html#a15). — hmjd, Jan 05 '12 at 16:50

score 9 · Accepted Answer · answered Oct 20 '12 at 03:42

9

NO, We need to call json_object_put only once for root object as long as we are not explicitly allocating memory to json-object and this worked for me.....!!

answered Oct 20 '12 at 03:42

Madhu S. Kapoor

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score 7 · Answer 2 · edited Mar 06 '12 at 03:51

7

Yes, I believe your code will leak memory. The problem is that you are overwriting your new_obj pointer multiple times. Your code should be something like this:

struct json_object *new_obj, *fuu_obj, *foo_obj;
new_obj = json_tokener_parse(strRawJSON);
fuu_obj = json_object_object_get(new_obj, "FUU");
if(NULL == new_obj){
    SYS_OUT("\nFUU not found in JSON");
    return NO;
}
foo_obj = json_object_object_get(new_obj, "FOO"); 
if(NULL == new_obj){
    SYS_OUT("\nFOO not found in JSON");
    return NO;
}
json_object_put(foo_obj);
json_object_put(fuu_obj);
json_object_put(new_obj);

Please let me know if this works for you. If you want more help, json-c has a reference count mode which can give you more information about objects. Let me know and I can elaborate on this more.

edited Mar 06 '12 at 03:51

Timothy Jones

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answered Mar 06 '12 at 03:41

benathon

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6

NO, We need to call json_object_put only once for root object as long as we are not explicitly allocating memory to json-object and this worked for me.....!! – Madhu S. Kapoor Mar 12 '12 at 16:11
2

Yes actually you are right. You only need to call put one time for the root object! – benathon Apr 05 '12 at 18:05

score 2 · Answer 3 · edited May 30 '19 at 07:11

2

json_tokener_parse() will create an object which must be deleted. in this case

json_object_put(new_obj);

is required.

edited May 30 '19 at 07:11

adiga

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answered May 30 '19 at 06:58

rakesh.sahu

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Memory Leak Using JSON-C

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