recompile everything after compiler upgrade? (was: Re: problem with function as argum

In article <cndeup$3m1$1@online.de>, helbig@astro.multiCLOTHESvax.de
(Phillip Helbig---remove CLOTHES to reply) writes:
 
>
> None of the above.  :-|
>
> I've finally found the problem.  Since compiling the NUMERICAL RECIPES
> code, I had upgraded the Fortran compiler.  After recompiling the
> NUMERICAL RECIPES stuff, the problem went away.  Thus, I was misled by
> an inappropriate error message.  I suppose the compiler should notice
> that it is trying to USE stuff which was compiled with an older,
> incompatible version of the compiler and issue a fatal error message in
> that case, saying that one should recompile.

Wouldn't it be a good idea for the standard to require that a compiler
give an error if it is accessing modules via USE compiled with a
previous version of the compiler?  It seems to me that the only
alternative is to recompile everything after each compiler upgrade,
since I'm sure the standard doesn't require the results of compiling
modules to be compatible for all versions of the compiler.

In my case, I got a strange error which forced me to track down the
problem.  But perhaps I could have gotten just a wrong answer, which
would have been worse due to the danger of not noticing it.

What do folks do?  Recompile everything you USE after upgrading the
compiler?  If not, does your compiler vendor guarantee compatibility?