[krbdev.mit.edu #5693] Problems using Intel C compiler on trunk builds

[Ken Raeburn via RT]

> There are several issues in using Intel's C compiler in building krb5.
> The compiler is "interesting" in that it pretends to look like the GNU
> compiler - by defining __GCC__ and other version specific defines.

Well that's kind of rude. :)  Unless it's actually based on gcc, but given that it seems to be 
licensed commercially or for personal use only (if I'm looking at the right web pages), I doubt 
that would be the case.

> Why would want to use icc instead of gcc? Well different compilers
> pick
> up different problems - and help improve portability.

Sure.  Maybe not enough for us to pay for the academic license, but if you've got it anyways, 
and can point us at specific problems....

> b) While icc does know a number of gcc -W constructs - it does not
> know
> all of them.  Instead of having a fatal error - it produces a warning.
> This results in four warnings per file compiled... Annoying but not
> fatal.

If you can tell me which ones, I can probably write a configure test to see if they work in a 
given compiler.  I assume adding -Werror will make it fatal, making the test fairly 
straightforward?  (Or, if you want to do it, I think the test for support for -Wno-format-zero-
length may be a good starting point.)

> c) The thread detection is giving warnings during configuration - and
> comparison on config.cache from icc and gcc build trees indicates that
> there may be some problems in detecting reentrant functions and thread
> support.

Hm, that's kind of annoying.  And hard to debug indirectly...