On Thu, Sep 20, 2018 at 11:25:27AM -0400, Steven Schveighoffer via Digitalmars-d wrote: > On 9/20/18 11:06 AM, H. S. Teoh wrote: [...] > > IIRC, originally the stacktrace was also built at exception > > construction time. But it was causing a major performance hit, so > > eventually someone changed the code to construct it lazily (i.e., > > only when the catcher actually tries to look it up). > > > > I think it makes sense to also make .msg lazy, if the exception > > object is already carrying enough info to build the message when the > > catcher asks for it. And if the catcher doesn't ask for it, we saved > > an extra GC allocation (which is a plus even if we're not trying to > > go @nogc). > > Except we DON'T construct the stack trace string, even lazily. If you > look at the code I posted, it's output directly to the output buffer > (via the sink delegate), without ever having allocated. > > I think we can do that for the message too (why not, it's all > supported). But either one (using GC at print time, or lazily > outputting to buffer at print time) solves the biggest problem -- > being able to construct an exception without the GC. [...]
Yeah, that's what I meant. :D Well, for backward compatibility we could still have .msg allocate and return a string, but we could provide an overload / alternate member function that writes directly to a sink instead. Then we don't ever have to allocate unless the sink itself does. T -- I am a consultant. My job is to make your job redundant. -- Mr Tom
