Parden me if I do not express my question very well.

A project I am considering would benefit greatly from the ability to to compile a dll at runtime, on machines which may or may not have appropriate tools installed (so I may be looking at using third party tools if available)

For example, User runs my executable, which creates a dll with a function they want to use, selected by them.
My executable adds the function(s) and compiles a dll and outputs a usage txt file.

My questions are: is there some sort of tool/portalbe app I could use to accomplish this? is there a proper name or term for what I am trying to accomplish?

Any tips or comments are very welcome.

What you're describing sounds like a compiler.

Indeed :) Thanks.

does anyone know of any stand alone compilers I might use in such a fashion?
Ideally which accepts command line.

Every compiler is command line driven.

In terms of a compiler that won't require your users to have to install it and all that junk, portable apps has a portable version of MinGW that probably requires less installation than other options.

If you're targetting a *nix system, you've got the existing configure scripts and you can assume they've got a compiler already.

Thank's I'll have a look at MinGW.
I'm targeting Windows >= Xp

Is this purely for the fun of it? It's really not common on Win to make the end user build the library themselves.

Not for fun, well not entirely.

user programs in some other language but wants to use a c/c++ dll from within that language, and does not know how.

there are a preset amount of functions they can choose from, when selected, a dll will be built with that functionality.

Would it not be easier to just build one with all the functions and give that to the user?

Yes, but eventually I intend to attempt to convert code from another language and dynamically create functions.

So perhaps my question boils down to help with compiling a dll through commandline using a third party compiler, the easiest to use etc, bearing in mind I've only ever compiled code through Visual studio IDE, so I don't even know where to start.

Thank you.
I don't understand why I never found that in my search.