c++ - I can't understand the deleteOwnedPtr function in Webkit -


in found function in webkit

template<typename t> inline void deleteownedptr(t* ptr) {     typedef char known[sizeof(t) ? 1 : -1];     if(sizeof(known))         delete ptr; }

why don't use

if (sizeof(t))     delete ptr;

what mean

char known[-1];

found explanation in webkit-dev mailing list. raises compiler errors if trying delete incomplete types.

https://lists.webkit.org/pipermail/webkit-dev/2010-november/015051.html

if delete pointer , object has incomplete type, undefined behavior. instead code causes compilation fail if object has incomplete type. use of negative number size of array way guarantee compilation error.


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