> On 22 May 2024, at 12:12, XChy <xxs_...@outlook.com> wrote: > >> How is the memset in select_rtable_names_for_explain a dead-store? Even >> memset calls could be optimized away from the EXPLAIN codepath I have a >> feeling it >> would have to be many in a tight loop for it to be measurable even?
> For the first question, I don't mean that the memset is the dead store. Gotcha > I mean that the stores with value "0" after the memset are dead: > ``` > dpns.subplans = NIL; > dpns.ctes = NIL; > dpns.appendrels = NULL; > ``` > since the memset has written zeroes to the object "dpns", and these members > are known to be zero. They are known to be zero, but that's not entirely equivalent though is it? NIL is defined as ((List *) NULL) and NULL is typically defined as ((void *) 0), so sizeof(0) would be the size of an int and sizeof(NULL) would be the size of a void pointer. -- Daniel Gustafsson
