I've been hunting around on why this compiles:

```
struct x_ {
    char a[10];
    int  b;
};

struct x_ tmp = {{{{0}}}};

```

We may have an older gcc version, so {0} may not work and {{0}} should be used, but don't see this {{{{0}}}} anywhere. 
See gcc bug here: <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53119>

Thanks
Peter