This chapter lists the backwards incompatible changes introduced in Jansson 2.0, and the steps that are needed for upgrading your code.
The incompatibilities are not dramatic. The biggest change is that all decoding functions now require and extra parameter. Most programs can be modified to work with 2.0 by adding a 0 as the second parameter to all calls of json_loads(), json_loadf() and json_load_file().
Jansson 2.0 is backwards incompatible with the Jansson 1.x releases. It is ABI incompatible, i.e. all programs dynamically linking to the Jansson library need to be recompiled. It’s also API incompatible, i.e. the source code of programs using Jansson 1.x may need modifications to make them compile against Jansson 2.0.
All the 2.x releases are guaranteed to be backwards compatible for both ABI and API, so no recompilation or source changes are needed when upgrading from 2.x to 2.y.
For future needs, a flags parameter was added as the second parameter to all decoding functions, i.e. json_loads(), json_loadf() and json_load_file(). All calls to these functions need to be changed by adding a 0 as the second argument. For example:
/* old code */ json_loads(input, &error); /* new code */ json_loads(input, 0, &error);
The underlying C type of JSON integers has been changed from int to the widest available signed integer type, i.e. long long or long, depending on whether long long is supported on your system or not. This makes the whole 64-bit integer range available on most modern systems.
jansson.h has a typedef json_int_t to the underlying integer type. int should still be used in most cases when dealing with smallish JSON integers, as the compiler handles implicit type coercion. Only when the full 64-bit range is needed, json_int_t should be explicitly used.