[cdt-dev] Programmatically excluding files from build "on-the-fly"

[Christian Walther <walther@xxxxxxxx>]

I am new to CDT, trying to write an extension for it, and hoping some  
of the experts here will be able to help me out with finding the best  
way of achieving my goal before I possibly invest too much work going  
in a suboptimal direction.

We are building a specialized IDE on top of CDT (currently CDT 7.0.1  
on Eclipse 3.6.1) for a C++ codebase whose characteristic it is that  
we have a number of source files always present on the file system,  
but only a subset of them, depending on various circumstances, needs  
to be compiled and linked into the build product for any given build  
(this is a requirement that cannot be changed).

Our current prototype achieves this by inserting another builder that  
runs before the CDT builder, evaluates the conditions to determine the  
subset of files to be built, and sets the source folders and exclusion  
patterns of the active configuration, i.e. the "exclude from build"  
setting of each file (these are the same thing, right?), accordingly.

This appears to work, but has a few disadvantages (not deal-breakers,  
but maybe there's a way of avoiding them):

- The source folders are persisted in the .cproject file, which means  
this file changes every time our subset changes (actually, it  
currently doesn't do that reliably, but that's something I need to  
fix, but haven't figured out how yet), creating unwanted diffs in  
version control. For our purposes, this information is redundant and  
doesn't need to be stored, since it is regenerated (from information  
stored elsewhere) on every build.

- Overwriting the "exclude from build" settings / source folders and  
exclude patterns means that users can't use them for their own  
purposes anymore, as their manual modifications will be wiped out at  
the next build. This is confusing at best and a loss of functionality  
at worst.

Is there a better way of achieving what I want? Ideally I would like  
to hook into the CDT makefile generator and tell it which files to  
consider on the fly, without clobbering any persistent user settings,  
but I haven't found any extension point that would allow me to do that  
- and replacing the entire thing looks like a daunting task.

 -Christian