From ef88f0e530b898ebcb14f9e3dff1d58e83089ada Mon Sep 17 00:00:00 2001
From: user <user@clank>
Date: Thu, 16 Jul 2026 00:49:58 +0200
Subject: C toolchain: run SDCC-compiled C programs as gbos processes

- c/{gbos.h,crt0.s,libc.s,build.sh}: SDCC sm83 -> ROM-bank blob toolchain.
  libc syscall wrappers save/restore BC/DE/HL around rst $30 (trap clobbers
  them; SDCC expects them preserved).
- build via SDCC native asxxxx path (sdasgb/sdldgb), crt0 linked first so
  _start is the $4000 entry; blob INCBIN'd into a ROM bank.
- chello.c: prints a message + getpid() -> runs as 'chello' shell command.
- Makefile: auto-build c/*.bin, track as a dep of programs.o; gitignore blobs.
- README: document the C toolchain + the SDCC --asm=rgbds codegen bug that
  forced the native-toolchain approach.
- verified: '$ chello' -> 'hello from C on gbos!' / 'my pid is 2'.
---
 Makefile | 7 +++++++
 1 file changed, 7 insertions(+)

(limited to 'Makefile')

diff --git a/Makefile b/Makefile
index 23551ad..ad14afd 100644
--- a/Makefile
+++ b/Makefile
@@ -17,6 +17,13 @@ all: $(ROM)
 $(BUILD)/%.o: src/%.asm | $(BUILD)
 	rgbasm $(ASFLAGS) -o $@ $<
 
+# C programs: compiled with SDCC into ROM-bank blobs and INCBIN'd by programs.asm
+CBLOBS := c/chello.bin
+$(BUILD)/programs.o: $(CBLOBS)
+
+c/%.bin: c/%.c c/crt0.s c/libc.s c/build.sh
+	sh c/build.sh $< $@
+
 $(ROM): $(OBJS)
 	rgblink -m $(BUILD)/gbos.map -n $(BUILD)/gbos.sym -o $@ $(OBJS)
 	rgbfix $(FIXFLAGS) $@
-- 
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