sys: Declare 'end' as an extern char[]

[jhb]

Summary

While here, remove an unused declaration.

Sponsored by: AFRL, DARPA

[jrtc27]

s/extern char/&[]/ in the subject, also &end is not char * in that case, it's char (*)[], which is an incomplete type so you can't perform pointer arithmetic on it (as sizeof(char[]) is not known). end itself decays to a char * and so pointer arithmetic on *that* works (or &end[0], but decaying is cleaner). In this case though there's an explicit cast before the arithmetic so both "work".

[jhb]

Ah, so you could use (char *)foo - end in place of the casts? But not &end?

[jhb]

Hmm, so does (vm_offset_t)&end still work after this change or should it instead drop the &?

[jrtc27]

In D53898#1237357, @jhb wrote:

Hmm, so does (vm_offset_t)&end still work after this change or should it instead drop the &?

&array and array have the same address, but different types (T (*)[] vs T *, or T [] if not decayed of course), so (vm_offset_t)&end should still work.