Thoughts about D

[Jonathan M Davis]

On Thursday, November 30, 2017 16:48:10 Adam D. Ruppe via Digitalmars-d 
wrote:
> On Thursday, 30 November 2017 at 16:12:04 UTC, H. S. Teoh wrote:
> > Which brings us to the implementation of assert() itself. What
> > about it makes it so big? I suspect most of the bloat comes
> > from throwing AssertError, which pulls in the stack-unwinding
> > code, which, if my memory is still up to date, suffers from
> > performance issues where it tries to construct the stacktrace
> > regardless of whether or not the catch block actually wants the
> > stacktrace.
>
> That's false, I changed that many years ago myself, unless the
> DWARF change involved that too, but I don't think so.
>
> What happens is the exception constructor walks the stack and
> copies the addresses to a local, static buffer. This is very fast
> - just walking a linked list and copying some void* into a
> void*[64] or whatever - and little code.
>
> The expensive part of formatting it to a string, actually looking
> up the debug info, parsing out the addresses, etc., is done
> lazily when it is printed, which occurs only on demand or right
> before the program terminates.

Yeah, that change was a _huge_ speedup. It had a significant impact on
std.datetime's unit tests.

- Jonathan M Davis