#!/bin/sh
# Build a gbos C program into a self-contained 16 KiB ROM-bank image.
# SDCC native toolchain; crt0 linked FIRST so _start is the $4000 entry.
# usage: usr/build.sh <prog.c> <out.bin>     (run from the repo root)
set -e
SRC="$1"; OUT="$2"; B=build/usr/obj
LIBDIR=/usr/share/sdcc/lib/sm83
mkdir -p "$B" "$(dirname "$OUT")"
sdasgb -o "$B/crt0.rel" usr/crt0.s
sdasgb -o "$B/libc.rel" usr/libc.s
sdcc -msm83 -c -Iusr usr/libc.c -o "$B/libc_c.rel"
sdcc -msm83 -c -Iusr "$SRC" -o "$B/prog.rel"
# link: crt0 first (=> _start at 0x4000), then libc, program, and sm83 lib.
# TRAP: only _CODE/_DATA have pinned bases. sm83.lib modules (long div/mod/
# shift helpers) link into their own areas, which sdldgb places after _DATA -
# i.e. code in the $A000 RAM window ("buffer too small" from makebin, or
# garbage at runtime). Don't use long division/shifts in programs; see
# usr/uptime.c for the inlined-arithmetic workaround.
sdldgb -n -m -w -j -i "$B/prog.ihx" \
       -b _CODE=0x4000 -b _DATA=0xa000 \
       -k "$LIBDIR" -l sm83 \
       "$B/crt0.rel" "$B/libc.rel" "$B/libc_c.rel" "$B/prog.rel"
makebin -Z -p "$B/prog.ihx" "$B/prog.bin"
dd if="$B/prog.bin" of="$OUT" bs=1024 skip=16 count=16 2>/dev/null
echo "wrote $OUT ($(wc -c < "$OUT") bytes); entry:"
grep -iE ' _start| _main' "$B/prog.map" | head -2