On Sun, Aug 30, 2015 at 03:36:27PM +1000, Bruce Evans wrote: > On Fri, 28 Aug 2015, Joerg Sonnenberger wrote: > > >On Fri, Aug 28, 2015 at 10:17:56PM +1000, Bruce Evans wrote: > >>>-static void die(int); > >>>+static void die(int) __dead2; > >> > >>Since the function is static, it is very easy for the compiler to see > >>that it doesn't return. > > > >But the compiler can't tell if it is the *intention* that the function > >never returns. The warning behavior exists because that can easily > >change with macros etc. > > The compiler should trust the programmer to write correct functions.
That's a good one. Programmers are notorious for one thing, which is not writing correct code. > >>Even gcc-4.2.1 does this by default, since > >>-O implies -funit-at-a-time for gcc-4.2.1. For clang, there is no way > >>to prevent this (except possibly -O0) since, since -fno-unit-at-a-time > >>is broken in clang. > > > >It is not broken. It is loadly ignored as unsupported. The very > >existance of the option in GCC has always been a concession to broken > >and badly written code, including of course GCC's own CRT. > > Unsupported == incompatible == broken. > > My use of this option can probably be reduced to -fno-toplevel-reorder, > but that is even more broken in clang (it and -ftoplevel-reorder are > "unknown arguments", while -fno-unit-at-a-time is an "unsupported > optimization", and -funit-at-a-time works). Neither -fno-unit-at-a-time nor -funit-at-a-time is an optimisation. Nothing in the standard suggests a specific ordering and well written programs don't make such assumptions. All use cases I have seen so far are miswritten and fragile and would be better served by using a different approach. This is no different from broken code requiring function calls in a sequence point to be executed in a specific order. Joerg _______________________________________________ svn-src-all@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
