"Tofu Ninja" wrote in message news:dtjqnyucskwnqjvks...@forum.dlang.org...
Question?
If an if condition throws or returns in its body is it ok for the
optimizer to 'assume' that the condition is false after and make
optimizations for it? If so then every one complaining that assert gets
removed in -release should really just be using enforce.
Yes. In fact, it's required that an optimizer do this in order not to be
considered garbage.
The possibility for the optimizer to make the same optimizations for
assert can be done for enforce, the only difference is that it does not
get removed in -release....
Not quite. With enforce, it is impossible (ignoring hardware or optimizer
errors) for the condition to be false if the enforce was not triggered.
Because the assert is not checked, the condition could be false and the code
could do something awful.
Also, the optimizer can only use the enforce's assumption _after_ it has
checked the condition. Since with assert it doesn't need to check, it can
go backwards and assume the previous code will never produce a value that
can violate the assertion.
if (y > 7) // x can't possibly be >= 5, so this can't be true
x = y + 1;
assert(x < 5);
if (y > 7) // the program will throw if >= 5, but that doesn't mean it can't
be true
x = y + 1;
enforce(x < 5);
Assert is much much more powerful.
