[TUHS] Subject: changes for modern -> v7 -> v6 -> v5

[TUHS] Subject: changes for modern -> v7 -> v6 -> v5

[Doug McIlroy]

> no conditional compilation so no way to make a truly universal version
> which works on everything.

If cc -I is there, it should be able to do the tailoring.

Also conditional compilation of non-declaration statements can
be replaced by regular if statements that typically can be
optimized away (though the old C compilers may not do so).


Incidentally, I would say that the use of conditional compilation
is evidence that the code is NOT truly universal, but has to be
specially adapted to various environments.

Doug

[TUHS] Subject: changes for modern -> v7 -> v6 -> v5

[scj]

>
> Incidentally, I would say that the use of conditional compilation
> is evidence that the code is NOT truly universal, but has to be
> specially adapted to various environments.
>

For the most part, I agree, but there are some exceptions.  For example,
bit fields in C/C++ are laid out using the byte ordering conventions of
the target machine.  This can make it nearly impossible to write low-level
code to drive, e.g., hardware or communication protocols without
conditional compilation.

Of course, you can always shift and mask.  The code becomes
incomprehensible, but identical for big- and little-endian.  For my money,
using bit fields leads to code that is clear and easy to debug, and the
obvious rationale of the conditional code makes it a winner.

Steve