assert semantic change proposal

[Walter Bright via Digitalmars-d]

On 8/3/2014 7:31 PM, John Carter wrote:
> Compiler users always blame the optimizer long before they blame their crappy code.
>
> Watching the gcc mailing list over the years, those guys bend over backwards to
> prevent that happening.
>
> But since an optimization has to be based on additional hard information, they
> have, with every new version of gcc, used that information both for warnings and
> optimization.

Recent optimization improvements in gcc and clang have also broken existing code 
that has worked fine for decades.

In particular, overflow checks often now get optimized out, as the check relied 
on, pedantically, undefined behavior.

This is why D has added the core.checkedint module, to have overflow checks that 
are guaranteed to work.

Another optimization that has broken existing code is removal of dead 
assignments. This has broken crypto code that would overwrite passwords after 
using them. It's also why D now has volatileStore() and volatileLoad(), if only 
someone will pull them.

I.e. silent breakage of existing, working code is hardly unknown in the C/C++ world.