Re: pluggable out-of-date (Was: non-recursive build question)

[Noel Yap]

David Boyce wrote:

> At 07:31 AM 4/30/2004, Noel Yap wrote:
> Or, since clearmake seems to be our pole star on this, consider that it 
> uses various special targets (e.g. .NO_DO_FOR_SIBLING, .NO_CONFIG_REC, 
> etc) to handle such fine-tuning. So I guess an alternate plugin style 
> would be a special target which tells make what discriminator to dlopen 
> and use for what targets. I'm sure there are other and probably better 
> interfaces as well.
>
> My main point is simply that a dlopen-ed discriminator function might be 
> the most open, and least intrusive, architecture. And that dlopen (and 
> the equivalent Win32 API which I think is called LoadLibrary) is what 
> underlies most classic plugin implementations in browsers, Apache, etc.

A special target, something like (but probably with a better syntax):

.UP_TO_DATE_CHECK: checker: %.mk: %.m

would do the trick, I think.

OTOH, I'd still want to be able to create these checkers within the makefile 
itself.

> Hmm. I haven't. Or more specifically I've often run into linker/loader 
> issues but they've generally turned out to be because this stuff can be 
> really complicated and I hadn't fully read or understood the manual, not 
> because of an actual bug. Are you saying there are actual crippling bugs 
> in the GNU/Linux loader (and what version?) or just that the arcana of 
> working with it might be too painful for general use? If so I'd counter 
> by saying that there are many quite robust technologies (Apache comes to 
> mind) which use this same technique and which run fine on Linux from 
> time immemorial.

The one I personally experienced was with gcc-2.96.  It's so bad that a patch is infeasible.  The fix is to upgrade to 3.2 although I've seen problems with this, too, but I didn't get a chance to create a minimal test for it so these problems may not be 
insurmountable.

The problems I've seen were with C++ code.  C linking/loading is probably way more stable.  Since GNU make is written in C, the problems with dynamically loading libraries shouldn't strike them from consideration although, personally, I would still prefer 
coding the checkers directly in the makefile (which includes shelling out and calling an executable).

Noel