On exceptions in D

[Dmitry Olshansky]

09-Feb-2014 22:14, Jakob Ovrum пишет:
> On Sunday, 9 February 2014 at 17:57:23 UTC, Dmitry Olshansky wrote:
>> void risef(T...)(string fmt, T args)
>> {
>>     static Failure!T slot;
>>     if(!slot)
>>         slot = new Failure!T();
>>     slot.assign(fmt, args);
>>     throw slot;
>> }
>
> If the template is instantiated we can say with almost certainty that
> the function will be called, so it'd be an improvement to allocate the
> exception instance statically (lazily initialized with emplace), instead
> of statically allocating just a reference to a GC-allocated instance.

Might be a good idea but compiler is pretty conservative with what can 
be created at compile-time and emplace may not play nice with CTFE.

> Also, it's nice to keep the throw statement in user code, e.g. `throw
> allocExf(fmt, args);`, as `throw` is a no-return statement like
> `return`, `assert(false)` etc.

Good idea. Then call it 'exception(f)' and use like this:
throw exceptionf("Message with some %s substitution", "writef-like");

-- 
Dmitry Olshansky