On Mon, Jul 11, 2005 at 09:58:36AM -0500, Nicholas Nethercote wrote: > Hi, > > There was recently a very long thread about the overflow behaviour of > signed integers in C. Apparently this is undefined according to the C > standard. I searched the standard on this matter, and while I did find > some paragraphs that described how unsigned integers must wrap around upon > overflow, I couldn't find anything explicit about signed integers. Can > someone point me to the relevant part(s) of the standard?
I don't have time to dig out all of the relevant sections, but I was on the ANSI X3J11 committee that defined the C standard from its beginning through the release of the C90 international standard (and some of the C99 work, though I left the committee before a lot of the changes were made). It did come up for discussion, but the committee did decide to leave it undefined, since there were C compilers for some different machines that did not just silently truncate. >From memory, there was one vendor with a machine that had signed magnitude integers. There was a vendor with a machine that had one's complement integers. I suspect at least one vendor used instructions that caused an overflow trap for signed arithmetic. -- Michael Meissner email: [EMAIL PROTECTED] http://www.the-meissners.org
