(j3.2006) Compilation cascades

[Van Snyder]

Van Snyder wrote:

> We compare .mod files to avoid compilation cascades.
> 
> I noticed that if I add a PRINT statement to a module procedure, several
> processors produce a different .mod file.
> 
> This seems a bit bizarre.  Is it really necessary?
> 
> Some processors put a time stamp in the .mod file, but we've figured out
> how to get around that.

Robert Corbett commented

! Some compilers put representations of the code for module procedures
! in the .mod files they generate.  This allows inlining module
! procedures, which are often short.  It is not necessary, but it can
! be a big performance advantage.  Of course, if you use such a compiler,
! the compilation cascades are pretty much necessary for correct
! operation.  If a module procedure that has been inlined has been
! modified, all files that include procedure references that
! reference one of the module procedures must be recompiled.

That would explain why the .mod file would be different no matter what
change I make.  Why would the .mod file be different only if I inserted
a PRINT statement (or deleted them all)?

-- 
Van Snyder                    |  What fraction of Americans believe 
Van.Snyder at jpl.nasa.gov       |  Wrestling is real and NASA is fake?
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