Add a test that triggers the problem to ensure it stays fixed.

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>

Also, there's no need to worry about output consistency here, since it'll be
 different anyway due to different pointer values.

Improve json_object -> string performance

Hawciz pointed out that the previous commit modifies the public
interface of printbuf. Per his suggestion, sprintbuf() was restored
and a new pair of macros was added that wraps printbuf_memappend().

Using a wrapper macro instead of modifying sprintbuf() also reduces
function call overhead, bringing total performance gains to
approximately 400%.

Removes variadic prints for ~3x performance improvement.

closes https://github.com/json-c/json-c/issues/278

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>

I got this on Mac OS X at least.
Not sure if it shows up in other envs

error:
```
strerror_override.c:53:13: error: incompatible redeclaration of library function 'strerror' [-Werror,-Wincompatible-library-redeclaration]
const char *strerror(int errno_in)
```

Signed-off-by: Alexandru Ardelean <ardeleanalex@gmail.com>

Json object set xxx

Conflicts:
	tests/test_util_file.c

Conflicts:
	tests/test_util_file.c

The test is implied in test1.

The idea is to check that the returned lengths and strings
are identical to what is expected to return the already
tested function 'json_object_to_json_string_ext'.

Signed-off-by: José Bollo <jose.bollo@iot.bzh>

Also, be sure the right locale_t is freed if we fail on the second uselocale.
Finally, fix test_locale so it *doesn't* use json_object_to_json_string as
 that will simple re-emit the original parsed string values.

The function fstat isn't declared without this include
on debian strect/sid and Fedora-23

Change-Id: I660a32ff173dcba04674aed51ed855b4fa55ac67
Signed-off-by: José Bollo <jose.bollo@iot.bzh>

Fix issues with the test script so it works under distcheck too.

Add tests and descriptions for the functions in json_util.c

To better distinguish between entry->k and entry->v being const within linkhash, but non-const outside, add lh_entry_v() and lh_entry_k() accessors.
Make lh_entry->k const.

Change %d to %llu and add cast to unsigned long long for size_t arguments,
otherwise compilation will fail with errors like:

test1.c:70:15: error: format ‘%d’ expects argument of type ‘int’, but argument 2 has type ‘size_t {aka long unsigned int}’ [-Werror=format=]

%zu is avoided to stay compatible with old libc versions (like old Visual
Studio).

The user might want to use the userdata for something different, so the
serializer should ignore it by default.

Explicitly setting the serializer to json_object_double_to_json_string will
still make it interpret the userdata as a format string.

Add utility function for comparing json_objects