[boost] Interlibrary version cchecking

Subject: [boost] Interlibrary version cchecking
From: Robert Ramey (ramey_at_[hidden])
Date: 2010-05-12 01:56:40

Turns out that the idea of a single boost library deployment has come up a 
couple of times here at BoostCon 2010.  While preparing my presentation I 
considered the problem of what would happen if one installed one library 
which depended on an newer version of a different library than the user 
already had installed.  I actually woke up in the middle of the night 
imagining someone would ask about that during my talk.  I puzzled about it 
for some time and the day before I found a way to address it - in my own 
mind at least.  It also seems that it turns out that there are tools that 
can also manage this.

It's not that I don't trust tools but I wear a belt AND suspenders.  So I 
would like a method which guarentees that when I build one library, I don't 
accidently include code from a prerequisite library which is a version so 
old that things won't work. I would also like to know that I'm not 
accidently running with a DLL built with an old version.

Basically each library includes a file "manifest.hpp".  This get's included 
when any header get's includes (once at most due to include guards).  This 
includes a static assert that checks that the prequiste libraries are of 
sufficiently recent version that a dependent library (or user application) 
requires.  There is also a manifest.cpp file included in the library which 
checks any prequiste DLLS.  This would be an exheedingly small overhead to 
avoid what could be an incredibly large headache.

I just verified that the code compiles so at this point it's only an idea. 
But it seems that some kind of check like this is un-avoidable of one want's 
to deploy libraries as needed rather than as a monolithic distribution.

FYI - no one asked me about this problem at my presentation.  Add one more 
confirmation of Murphy's law.

Robert Ramey

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`
end

begin 666 manifest.hpp
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`
end

begin 666 manifest.cpp
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`
end