> Robert Dewar wrote: > > People always say this, but they don't really realize what they are > saying. This would mean you could not put variables in registers, and > would essentially totally disable optimization.
- can you provide an example of a single threaded program where the assignment of variable to a machine register validly changes its observable logical results? > The -O2 flag is exactly a request to do optimizations that may cause > wrong programs to generate different results. - well this is certainly an interesting definition of -O2; and implicit definition of any program which invokes an undefined behavior as being "wrong"; as opposed to being arguably more accurately non-portable; as the standard enables compilers to specify a well defined behavior to that otherwise specified as being undefined. (nor seemingly particularly clever, as intentionally invoking a behavior not previously expressed seems like a great way to silently inject bugs into a program debugged utilizing lesser degrees of optimization as is typically done.)
