On Fri, May 17, 2019 at 7:59 PM Linus Torvalds <torva...@linux-foundation.org> wrote: > > On Fri, May 17, 2019 at 2:25 AM Miguel Ojeda > <miguel.ojeda.sando...@gmail.com> wrote: > > > > + memset((char *)(iter) + offsetof(struct trace_iterator, seq), 0, > > + sizeof(struct trace_iterator) - > > + offsetof(struct trace_iterator, seq)); > > Honestly, the above is nasty. > > Whenever you have to split an expression or statement over several > lines, you should ask yourself why it's so complicated.
Will do -- I was trying to keep the code as closely to the original as possible (I simply replaced the &iter.seq expression :-) By the way, how do you all feel about moving this as a generic facility to zero out the suffix/prefix of an structure? In particular, since we won't have the LAT* stuff according to Steven. > Also, the while 'offset' is a variable, any compiler will immediately > see that it's a constant value, so it's not like this will affect the > generated code at all. I like C++'s constexpr (for variable defs), maybe one day we will get it on C; it is useful to cleanly annotate compile-time values like this. > Unless you compile with something crazy like > '-O0', which is not a supported configuration exactly because we > expect compilers to not be terminally stupid. Fun fact: it seems clang folds some of these even under -O0. In godbolt I see it folding the third argument completely. The first one isn't, but it is computed on the function prologue, leaving the 'offset' variable unused. Cheers, Miguel
