const, volatile, etc [was Re: #defines with parameters]

[Guy Harris]

>...but what am I to do about fixing all the old stuff that now has
>subtle errors caused by optimizations that used to be illegal?

Back off on the optimization level, if your compiler will let you?  I
think the SunOS optimizer is generally "safe" at level -O2 (that's the
default level on Sun-4s, and only a very few modules crank it lower -
mostly things like bitblt code, not e.g. all the kernel or all the
device drivers):

     -O[level] Optimize the object code.  Ignored when either -g,
               -go,  or  -a is used.  On Sun-2 and Sun-3 systems,
               -O with the level omitted is equivalent to -O1; on
               Sun-4  systems,  it  is  equivalent  to  -O2.   on
               Sun386i systems, all levels are  the  same  as  1.
               level is one of:

                    1    Do postpass assembly-level  optimization
                         only.

                    2    Do global  optimization  prior  to  code
                         generation,        including        loop
                         optimizations,   common    subexpression
                         elimination,   copy   propagation,   and
                         automatic register allocation. -O2  does
                         not  optimize  references  to or defini-
                         tions of external or indirect variables.

                    3    Same  as  -O2,  but  optimize  uses  and
                         definitions  of external variables.  -O3
                         does not trace the  effects  of  pointer
                         assignments.  Neither -O3 nor -O4 should
                         be used  when  compiling  either  device
                         drivers,  or programs that modify exter-
                         nal   variables   from   within   signal
                         handlers.

                    4    Same as -O3, but trace  the  effects  of
                         pointer assignments.

I suspect some compilers can be told to back off to a safer level as well.