From 7759a52eb0ee980efd8a1d9faa1c84af1db1368c Mon Sep 17 00:00:00 2001
From: "B. Watson" <yalhcru@gmail.com>
Date: Thu, 18 Feb 2016 05:16:36 -0500
Subject: use custom stripped-down crt0 for cartridge, save 65 bytes

---
 Makefile    |  4 ++--
 crt0_cart.s | 72 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 74 insertions(+), 2 deletions(-)
 create mode 100644 crt0_cart.s

diff --git a/Makefile b/Makefile
index 8bac370..74ec7a5 100644
--- a/Makefile
+++ b/Makefile
@@ -314,8 +314,8 @@ mkcart: mkcart.c
 #	tail -c+2 taimain.xex > romable_taimain.raw
 #	rm -f taimain.xex
 
-romable_taimain.raw: $(TAIMAIN_C_SRC) $(TAIMAIN_ASM_SRC) $(TAIMAIN_HDRS) $(BIGNUM_SRC) $(BIGNUM_HDRS) $(TAIMAIN_LIBS)
-	cl65 --config cartbank3.cfg -m taipan.map -t atari -T -I. -L. -DFONT_ADDR=0x9c00 --start-addr 0x3ff -Wl -D__STACKSIZE__=0x200 -O -Wl -D__SYSTEM_CHECK__=1 -Wl -D__AUTOSTART__=1 -Wl -D__EXEHDR__=1  -DCART_TARGET=1 --asm-define CART_TARGET=1 -DBIGNUM=BIGFLOAT -o romable_taimain.raw.in $(TAIMAIN_C_SRC) $(TAIMAIN_ASM_SRC) $(BIGNUM_SRC) $(TAIMAIN_LIBS)
+romable_taimain.raw: $(TAIMAIN_C_SRC) $(TAIMAIN_ASM_SRC) $(TAIMAIN_HDRS) $(BIGNUM_SRC) $(BIGNUM_HDRS) $(TAIMAIN_LIBS) crt0_cart.s
+	cl65 --config cartbank3.cfg -m taipan.map -t atari -T -I. -L. -DFONT_ADDR=0x9c00 --start-addr 0x3ff -Wl -D__STACKSIZE__=0x200 -O -Wl -D__SYSTEM_CHECK__=1 -Wl -D__AUTOSTART__=1 -Wl -D__EXEHDR__=1  -DCART_TARGET=1 --asm-define CART_TARGET=1 -DBIGNUM=BIGFLOAT -o romable_taimain.raw.in $(TAIMAIN_C_SRC) $(TAIMAIN_ASM_SRC) $(BIGNUM_SRC) $(TAIMAIN_LIBS) crt0_cart.s
 	tail -c+2 romable_taimain.raw.in > romable_taimain.raw
 	rm -f romable_taimain.raw.in
 
diff --git a/crt0_cart.s b/crt0_cart.s
new file mode 100644
index 0000000..ec3e423
--- /dev/null
+++ b/crt0_cart.s
@@ -0,0 +1,72 @@
+;
+; Startup code for cc65 (ATARI version)
+;
+; Contributing authors:
+;       Mark Keates
+;       Freddy Offenga
+;       Christian Groessler
+;       Stefan Haubenthal
+;
+
+        .export         __STARTUP__ : absolute = 1      ; Mark as startup
+        .export         _exit, start
+
+        .import         initlib, donelib
+        .import         callmain, zerobss
+        .import         __RESERVED_MEMORY__
+        .import         __RAM_START__, __RAM_SIZE__
+        .include        "zeropage.inc"
+        .include        "atari.inc"
+
+; ------------------------------------------------------------------------
+
+.segment        "STARTUP"
+
+        rts     ; fix for SpartaDOS / OS/A+
+                ; They first call the entry point from AUTOSTRT; and
+                ; then, the load address (this rts here).
+                ; We point AUTOSTRT directly after the rts.
+
+; Real entry point:
+
+start:
+
+; Clear the BSS data.
+
+        jsr     zerobss
+
+; Setup arg stack
+        lda MEMTOP
+        sta sp
+        lda MEMTOP+1
+        sta sp+1
+
+; Call the module constructors.
+
+        jsr     initlib
+
+; Set the left margin to 0.
+
+        ldy     #0
+        sty     LMARGN
+
+; Set the keyboard to upper-/lower-case mode.
+
+        ldx     SHFLOK
+        sty     SHFLOK
+
+; Push the command-line arguments; and, call main().
+
+        jsr     callmain
+
+; Call the module destructors. This is also the exit() entry.
+
+_exit:  jsr     donelib         ; Run module destructors
+
+; Back to DOS.
+
+        rts
+
+; *** end of main startup code
+
+; ------------------------------------------------------------------------
-- 
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