Salted sha512 in C, cannot synchronise with Symfony2's FOSUserBundle

Salted sha512 in C, cannot synchronise with Symfony2's FOSUserBundle

My developement is separated into two components :
The website, a Symfony application using FOSUserBundle, which encrypts
password using SHA512, and a salt.
An authentication module, programmed in C, which should be able to
reproduce the SHA512 salted hash once it's given the salt, and the
cleartext password.
My problem occurs in the authentication module : I'm unable to get the
same hash as the one produced by Symfony's FOSUserBundle. Here's my
example :
The password salt, used by Symfony, is bcccy6eiye8kg44scw0wk8g4g0wc0sk.
The password itself is test
With this information, Symfony stores this final hash :
fH5vVoACB4e8h1GX81n+aYiRkSWxeu4TmDibNChtLNZS3jmFKBZijGCXcfzCSJFg+YvNthxefHOBk65m/U+3OA==
Now, in my C authentication module, I run this piece of code (crypt.h is
included) :
char* password = "test";
char* salt = "$6$bcccy6eiye8kg44scw0wk8g4g0wc0sk";
char* hash = malloc(256);
memset(hash, 0, 256);
encode64(crypt(password, salt), hash, strlen(password));
fprintf(stdout, "%s\n", hash);
(here is my base64 encoder :
http://libremail.tuxfamily.org/sources/base64-c.htm)
And this outputs...
JDYkYg==
Which is completely different from my Symfony2 hash.
Browsing Stack Overflow, I found this question (Symfony2 (FOSUserBundle)
SHA512 hash doesn't match C# SHA512 hash) written by someone encountering
the same issue (with C# though). So I decided to run this test...
char* password = "test{bcccy6eiye8kg44scw0wk8g4g0wc0sk}";
char* salt = "$6$bcccy6eiye8kg44scw0wk8g4g0wc0sk"; // I tried without
salt, or with "$6$" as well.
char* hash = malloc(256);
memset(hash, 0, 256);
encode64(crypt(password, salt), hash, strlen(password));
fprintf(stdout, "%s\n", hash);
Of course, it was a complete failure, I got :
JDYkYmNjY3k2ZWl5ZThrZzQ0cyRycmN6TnpJUXFOYU1VRlZvMA==
I've tried mixing the password and the salt in various ways, but I could
never get the Symfony's salt in the authentication module. Is there
something I've missed on the way ?