... is an extension provided by GCC

https://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html#Designated-Inits

To initialize a range of elements to the same value, write [first ... last] = value . This is a GNU extension. For example,

&& is another extension

https://gcc.gnu.org/onlinedocs/gcc/Labels-as-Values.html#Labels-as-Values

You can get the address of a label defined in the current function (or a containing function) with the unary operator && . The value has type void * . This value is a constant and can be used wherever a constant of that type is valid. For example: