Works with gcc, not with Arduino. error: taking address of temporary array
It is quite right, using that kind of syntax is not allowed. It's a bit of a pain, but it's ok since there is an alternative method - kind of a "trick" if you will.

That trick is to use a string, not an array. After all, a string is just an array, it's just handled slightly differently by the compiler.

Instead of using {...} use "..." and use the hexadecimal character escape sequence \xNN, such as:

cpaddr(a, "\x00\x10\xFF\xCA\x00\x00\xA2\x7D");


You could even lose your custom function and use a standard library function - memcpy():

memcpy(a, "\x00\x10\xFF\xCA\x00\x00\xA2\x7D", 8);


On the 8-bit AVRs you can save RAM by using the progmem variant and the F() macro:

memcpy_P(a, F("\x00\x10\xFF\xCA\x00\x00\xA2\x7D"), 8);