I observed this behavior with KeyFile.get_groups().

Vala testcase:

extern string[] get_strings ();

void print_string_count () {
    message ("string count: %d", get_strings ().length);
}

Generated code (in both 0.7.4 and 0.7.6~git, as of 2009/09/01):

char** get_strings (int* result_length1);
void print_string_count (void);
static void _vala_array_destroy (gpointer array, gint array_length, GDestroyNotify destroy_func);
static void _vala_array_free (gpointer array, gint array_length, GDestroyNotify destroy_func);



void print_string_count (void) {
        gint _tmp1__length1;
        char** _tmp1_;
        gint _tmp0_;
        _tmp1_ = NULL;
        g_message ("array-return-test.vala:4: string count: %d", _tmp0_);
        _tmp1_ = (_vala_array_free (_tmp1_, _tmp1__length1, (GDestroyNotify) g_free), NULL);
}

// definitions for _vala_array_destroy and _vala_array_free

If you replace the message() statement above with the following code, it emits the correct C:

    string[] res;

    res = get_strings ();
    message ("string count: %d", res.length);