>2. main() must return int in ansi compliant code for hosted environments.

the kernel isn't "hosted".  it *is* the host.

>3. Hosted/self-hosted cannot be determined at compile time (unless gcc has a 
>flag for this), so 2 must always be true (the compiler must assume the 
>program is hosted).

kernels are built with -ffreestanding on the 1.6 branch and in
-current.  the gcc man page says:

       -ffreestanding
              Compile for a freestanding  environment;  this  im-
              plies  the  `-fno-builtin' option, and implies that
              main has no special requirements.

which sounds like the flag you are looking for.

>4. Since self-hosted code will probably never return (but calling exit() 
>makes it return!), this technicality may not matter anyway.

i *suppose* the kernel could return, but that would be to the boot
blocks, whose only response might...reboot?  "never test for an error
condition you're not prepared to handle."

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