Re: [TUHS] Unix stories

"Ron Natalie" <ron(a)ronnatalie.com> wrote: |There's a trademark between allowing the compiler to reorder things \ |and having a defined order of operations. |Steps like that are well-defined in Java for instance. C lets the \ |compiler do what it sees fit. | |Note that it's not necessarily any better in assembler. There are \ |RISC architectures where load-followed-by-store and vice versa may \ |not always be valid if done in quick succession. Requiring the compiler \ |to insert sequence points typically wastes a lot of cycles. Assembler \ |programmers tend to think about what they are doing, the C compiler \ |tries to do some of this on its own and its not clairvoyant. I have just read again Clive Feather's ISO/IEC JTC1/SC22/WG14 N925 draft on sequence points, and i seem to be wrong about especially the shown exampl,e and Random knew that earlier. I first read that document in the context of aliasing issues a few years back, when i saw some BSD changesets fly by, and i remember a thread on a FreeBSD list, too, where objects backing pointers could no longer be accessed directly, but first need to be copied over to some -- then newly introduced -- local scope storage before being used, because of new aliasing rules of the C language. It seems i hyperventilated in the sequence point document back then. --steffen