Darren New <dne### [at] sanrrcom> wrote:
> I've always wondered why people think C is good for writing kernel-level 
> code, as the only facility in C that actually deals with the sorts of things 
> you do in a kernel is "volatile".

  Because C allows many types of low-level optimization that are very
difficult, if not even outright impossible, in higher-level languages.

  For example, you know how a C struct will map onto memory locations,
on every possible platform which your kernel can be compiled for. You know
exactly what assigning one struct instance to another entails as machine
code. If you need a pointer which should point to a raw memory address,
you can create one. You can be sure that something like garbage collection
will *not* suddenly and unexpectedly kick in during a highly-critical
operation. If needed, you can even write inline-asm for things which cannot
be done in C directly (eg. write or read from ports, issue some exotic CPU
commands such as disabling interrupts, etc).

  And of course C allows for programmatical optimizations which can often
be difficult in higher-level languages. Memory usage optimization would be
the main example. In something like a kernel you really don't want to waste
too much memory if you don't have to.

-- 
                                                          - Warp

Post a reply to this message