long names in C programs

[VLD/VMB]

Sounds like you're not exerting enough control over the contract
C programmers.  Plum-Hall publishes some excellent guideline documents
that you could require conformance to.  For one's own purposes,
Harbison & Steele do a good job of making recommendations for
portability in their "C: A Reference Manual".

I agree that the default behavior of a C programmer should be to
code portably, except when there is a demonstrable problem doing so.
Unfortunately, most recent college grads have not been exposed to a
wide enough range of systems to really understand what the portability
issues are, so they should rely on guidelines published by those who do.