FABRIC.md item 4.5d: GCC's -O2 folds putchar(c)/fputc(c,stdout) call sites
into putc(c,stdout), and getchar() into getc(stdin) -- neither symbol was
ever needed at -O0 because that fold pass is inactive there. Both are thin
wrappers reusing the existing putchar()/getchar() implementations exactly
(putc -> console_putc via putchar; getc -> the existing "no stdin in
kernel" -1/EOF stub via getchar), not new behavior.
Harmless at the current -O0 build (nothing calls these symbols directly at
-O0); this is prep for enabling optimization, verified against a clean
amd64 boot at unchanged -O0.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
sf_mutex_lock()'s no-op is correct only while nothing in interrupt
context mutates the structure a given lock protects. States that
explicitly, and states why a real spinlock is the wrong fix if that
constraint is ever violated: a single hart would deadlock spinning
against its own interrupt handler. The correct fix in that case is
disabling interrupts around the critical section.
Documentation only, no behaviour change.
Punch list §25 item 0.9 complete.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
