Something scary for halloween

[brooksmoses]

So, I discovered something scary this evening, as appropriate for the holiday. (Well, scary, for those of you who know C++, anyhow.)

I was tracking down a segfault in a testcase for our rather heavily template-based C++ library, and decided that the obvious thing was to run it in GDB and have a look at the stack trace.

I present to you just a tiny -- but telling -- piece from the middle of the ten-thousand-character result I got from "where":

  vsip::impl::None_type> > > > > > > > > > > > >, false>::exec

Comments

[pure-agnostic.livejournal.com]

A template 14 layers deep?

Luckily, you can find some utilities on the web which will decode C++ compiler error messages that contain templates.

[mayaknife.livejournal.com]

Ugh.

I'm always impressed by the tricks that people like Andrei Alexandrescu can do with C++ templating, but it also seems to me that when that much cleverness is required to do what are ultimately relatively simple tasks, then the there's something wrong with the language.

[zwol.livejournal.com]

Knowing what's going on there, I wonder, if you took that library and reimplemented it in a language with a sane metaprogramming facility ... would it get any more debuggable? I am actually thinking it wouldn't. You might not have the heinous parse-tree-in-the-type-system, but the construct seen by the code generator would still bear only a sketchy resemblance to the source.