On 3/1/18 3:24 PM, ag0aep6g wrote:
On Thursday, 1 March 2018 at 20:14:07 UTC, Steven Schveighoffer wrote:
dmd -version=dosafe -noboundscheck -run testarrayoverlap.d => no
error, undefined behavior
dmd -run testarrayoverlap.d => error
@safe has nothing to do with it.
@safe has everything to do with. @safe guarantees that there's no
undefined behavior. If you can trigger UB in @safe code, that's a bug.
The guarantee must hold whether asserts are enabled or not.
-noboundscheck does not just disable asserts, it undermines @safe,
rendering it meaningless.
Yeah, it seems like -noboundscheck should never be used.
It's undefined behavior if the check is disabled. How you get the check
disabled may be affected by @safe, but whether it's UB or not has
nothing to do with @safe. It has to do with "I turned off the checks".
Basically, in D, if your program *would have* thrown an Error, but
didn't because you turned it off, the compiler is free to assume UB.
For just disabling asserts (without affecting @safe), there's -release.
With your same code, `dmd -release` => UB, but `dmd -release
-version=dosafe` => Error.
I was unaware that it would work this way. I thought it would be the
same whether you used @safe or not with -release.
-Steve
