Initial commit: C64 project skeleton with oscar64 submodule

src/build.sh

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+#!/bin/sh
+# build.sh — compile and optionally run a single C64 program with Oscar64.
+#
+# Usage:
+#   ./build.sh            # compile helloworld.c → build/helloworld.prg
+#   ./build.sh -e         # compile, then run in the oscar64 built-in emulator
+#   ./build.sh -c         # just compile (default; -c is a no-op for clarity)
+#
+# Output (in ./build/):
+#   helloworld.prg   — loadable C64 program (run with x64, VICE, or real hw)
+#   helloworld.asm   — full 6502 listing
+#   helloworld.map   — region/section/object placement
+#   helloworld.lbl   — VICE monitor label commands
+
+set -e
+
+# --- locate the oscar64 compiler -----------------------------------------
+# This script is ./src/build.sh, so the repo root is one level up.
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+ROOT="$(cd "$SCRIPT_DIR/.." && pwd)"
+OSCAR64_DIR="$ROOT/oscar64"
+OSCAR64_BIN="$OSCAR64_DIR/bin/oscar64"
+BUILD_DIR="$SCRIPT_DIR/build"
+
+# Output goes in ./build/ (relative to the src dir), kept out of the source tree.
+mkdir -p "$BUILD_DIR"
+
+# Build the compiler if the binary is missing. (make -C make is the
+# makefile-based build from the upstream oscar64 source tree.)
+if [ ! -x "$OSCAR64_BIN" ]; then
+	echo "oscar64 compiler not found at $OSCAR64_BIN; building it..."
+	( cd "$OSCAR64_DIR" && make -C make compiler )
+fi
+
+if [ ! -x "$OSCAR64_BIN" ]; then
+	echo "error: $OSCAR64_BIN is still missing after build" >&2
+	echo "  try: cd $OSCAR64_DIR && make -C make compiler" >&2
+	exit 1
+fi
+
+# --- compile + optionally run --------------------------------------------
+SRC=helloworld.c
+EMU_FLAGS=""
+
+for arg in "$@"; do
+	case "$arg" in
+		-e) EMU_FLAGS="-e" ;;
+		-c) ;;  # explicit compile-only, no extra flags
+		-*) echo "unknown flag: $arg" >&2; exit 1 ;;
+	esac
+done
+
+echo "compiling $SRC with $OSCAR64_BIN -> $BUILD_DIR/"
+# -o puts the .prg in the build dir; the other artifacts (.asm, .map, .lbl)
+# follow automatically since they share the base name.
+"$OSCAR64_BIN" -i="$OSCAR64_DIR/include" -o="$BUILD_DIR/helloworld.prg" "$SRC"
+
+if [ -n "$EMU_FLAGS" ]; then
+	echo "running helloworld.prg in oscar64's built-in emulator"
+	# The emulator reads the .prg; re-run with -e pointing at the same output.
+	"$OSCAR64_BIN" -i="$OSCAR64_DIR/include" -o="$BUILD_DIR/helloworld.prg" -e "$SRC"
+fi
+
+echo "done: $BUILD_DIR/helloworld.prg"

src/helloworld.c

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+// helloworld.c — minimal C64 program in C with Oscar64
+//
+// Builds a .prg that prints "Hello World" on the C64 text screen and exits.
+//
+// Build:  ../scripts/build.sh
+// Run:    x64 helloworld.prg   (or use ../scripts/build.sh -e to run in
+//                              the built-in oscar64 emulator)
+
+#include <stdio.h>
+
+int main(void)
+{
+	// CHR$(147) is PETSCII "clear screen" — same as printf("\f") in C but
+	// emitted as the right byte for the C64's PETSCII character set.
+	putchar(147);
+
+	// The p"" prefix tells Oscar64 to emit the string as PETSCII, not ASCII.
+	// Without it the C64's character ROM would render garbage because the
+	// character generator maps 'H' to PETSCII 8, not ASCII 72.
+	printf(p"Hello World\n");
+
+	return 0;
+}