[boost] Template Metaprogramming I/O (well, O anyway)

From: David Greene (greened_at_[hidden])
Date: 2004-12-27 14:44:48

I asked this question a year or two ago on the list.

Has anyone come up with a good way to dump template metaprogramming
information at compile time?  I'd like to be able to do this both
in a "print" sense (compiler warnings) and an "error" sence (compiler
abort).

I hacked something together last week that sort of does the job.
There's a print<Message, FileLine> class that has a constructor with
an unused variable declared.  gcc gives a nice warning with -Wall.
I also have some hacked macros to pass file and line number information
to the printer.

The printer will dump a warning if its constructor is ever instantiated.

The use of all this appears in my last post in the "Named Template
Parameters" thread.

But this is really terrible.  I don't like it much so I'm hoping
someone else has a better solution.  In particular, it's almost useless
if there are any errors in the code because compilation will stop
before instantiation happens.  Unfortunately, this is _exactly_ the
case where one really wants to get this information and figure out
what's causing the compiler abort.

I know this is useful functionality, practically required for any
large metaprogramming project.  I'd like to see if Boost can make
something really good.

                          -Dave