On Tuesday, 4 August 2015 at 21:07:20 UTC, Steven Schveighoffer
wrote:
On 8/4/15 4:56 PM, Jonathan M Davis wrote:
On Tuesday, 4 August 2015 at 20:48:52 UTC, Steven
Schveighoffer wrote:
On 8/4/15 4:43 PM, Steven Schveighoffer wrote:
I should say, any assert(0) with a message printed that is
possible to
trigger in release mode is an error. If you can ensure it's
only
possible to trigger when compiled in debug mode (or for unit
tests),
then assert(0, msg) is fine.
In that vein, would it be possible to make this a warning?
i.e. if you
compile a file in -release mode, and the compiler encounters
an
assert(0, msg), it emits a warning?
I fail to see why it's a problem if assert(0) has a message.
It's
exactly the same as any other assertion except that it stays
even with
-release, and you don't get the message then (whereas with a
normal
assertion, you wouldn't get anything).
Seeing an assert with a message gives the impression that you
will see the message if you get there. I get that normal
asserts may not even trigger. But the concept of "oh, if I see
that message I know what happened" really goes out the window
if you are never going to see it.
As I said earlier, any line in druntime that has an assert(0,
msg) is a bug, because the message is never seen.
It stills indicate why the assertion is there, which can be
helpful to maintainers, and it _is_ possible to build druntime in
debug mode. It's just not released that way (though it's been
argued before that druntime/Phobos should be released with both
debug and release builds).
And arguing against assert(0) with a message in druntime because
it's not going to show the message normally would basically be
the same as arguing against having any assertions in there at
all, because they wouldn't show up in a typical build either. But
that doesn't mean that they shouldn't be there, just that they're
not as useful as they might otherwise be, because druntime is
almost always built in release mode.
Doing the static if thing isn't the right answer either. The
right answer is to choose one or the other (and by choosing to
print a message, you could either throw an assert error
directly, or print the message specifically and then assert(0)
).
So basically:
assert(0, msg);
becomes
printSomehow(msg);
assert(0);
With druntime it's difficult to actually print the message (and
my PR is trying to fix that).
I really so no difference between having a message with an
assert(0) as with any other assertion. You're not going to see
either with -release. It's just that assert(0) kills your program
instead of giving you undefined behavior.
I'm certainly not opposed to have a message be printed before the
HLT instruction with assert(0), but I don't at all agree that the
fact that the message is not seen in -release is a reason not to
have a message.
- Jonathan M Davis
