On Wed, 23 May 2007, Derek M Jones wrote: > > > > passes with -pedantic -std=c99. Replacing that with 1 + n - n + n - n > > is still OK with gcc; 1 + n + n - n - n is not. > > > > So that's hardly an example of, well, anything. > > It is an example of order of evaluation mattering when overflow > occurs. No it isn't. "1 + n - n" can overflow equally as "1 + n + n - n -n" can, and if you want them to do saturation or something, you cannot optimize _either_ of them to just "1". If "n" is MAX_INT, then with saturating arithmetic, neither of them results in 1. Not that signed overflow is even specified by the C standard (and unsigned is specified to be well-behaved). So it seems to be purely a compiler misfeature. No excuses. Linus - To unsubscribe from this list: send the line "unsubscribe linux-sparse" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
