Re: Building multiple configurations?

[Michael Ekstrand <michael@elehack.net>]

On 03/22/2010 07:35 PM, Grant Olson wrote:
> I'm doing something weird here and I'm thinking there has to be a better
> way.
> 
> I've got a configuration file that's a .ml file.  And I do want it to be
> an .ml file that gets included at compile time, not some .txt config
> file that gets read in at runtime.  I'm building two different versions
> of my app, with two different configurations.
> 
> Basically, I want to do the same thing as a C #ifdef:
> 
> #ifdef VERSION2
>    ... include version one
> #else
>    ... include version two
> #endif

You can get that kind of behavior, albeit in a bit more restricted
fashion, with the camlp4.macro syntax extension.  It provides DEFINE,
IFDEF, etc.

> And then the two different builds link in two different object files
> that have the same interface, creating the two different versions of the
> app.
> 
> At first I thought I could write out the "module" and "module type"
> stuff manually, giving the same module name in two differently named
> files.  But this of course creates a sub-module that isn't bound to the
> right namespace, and linking fails.

You could also have the two different module implementations under
different names and have the build system symlink or copy the correct
one in place prior to building.  In OMake, this is easy with the
'ln-or-cp' command.

- Michael