From 29b51c0dfdd27de76b489cd77ea70d25d9d74fdc Mon Sep 17 00:00:00 2001
From: "B. Watson" <urchlay@slackware.uk>
Date: Mon, 13 Apr 2026 06:24:18 -0400
Subject: Zero the BSS in the throwaway STARTUP segment. 7764 bytes free.

---
 src/crt0.s | 41 +++++++++++++++++++++++++++++++++++++++--
 src/main.c |  2 --
 2 files changed, 39 insertions(+), 4 deletions(-)

(limited to 'src')

diff --git a/src/crt0.s b/src/crt0.s
index 44a1c93..564ca3d 100644
--- a/src/crt0.s
+++ b/src/crt0.s
@@ -13,10 +13,13 @@
         .export         __STARTUP__ : absolute = 1      ; Mark as startup
         .export         _exit, start
 
-        .import         _main, zerobss
+        .import         _main;  not any more: , zerobss
         .import         __RESERVED_MEMORY__
         .import         __MAIN_START__, __MAIN_SIZE__
         .import         __LOWCODE_RUN__, __LOWCODE_SIZE__
+        .import         __BSS_RUN__, __BSS_SIZE__
+        .import         _scr_init, _init_channels
+        .importzp       ptr1
         .include        "zeropage.inc"
         .include        "atari.inc"
 
@@ -35,7 +38,36 @@
 start:
 
 ; Clear the BSS data.
-        jsr     zerobss
+; This routine was copied from libsrc/common/zerobss.s.
+;zerobss:
+        lda     #<__BSS_RUN__
+        sta     ptr1
+        lda     #>__BSS_RUN__
+        sta     ptr1+1
+        lda     #0
+        tay
+
+; Clear full pages
+
+L1:     ldx     #>__BSS_SIZE__
+        beq     L3
+L2:     sta     (ptr1),y
+        iny
+        bne     L2
+        inc     ptr1+1
+        dex
+        bne     L2
+
+; Clear remaining page (y is zero on entry)
+
+L3:     cpy     #<__BSS_SIZE__
+        beq     L4
+        sta     (ptr1),y
+        iny
+        bne     L3
+
+L4:
+; Done clearing BSS.
 
 ; Set up the stack
         lda MEMTOP
@@ -50,6 +82,11 @@ start:
         sty     SHFLOK          ; Turn off Caps Lock
         sty     SOUNDR          ; Turn off SIO beep/click
 
+; These 2 used to be called from main(). Moving the calls here saves 6 bytes.
+; Do not call _edbox_clear from here (we're *running* in the edbox area).
+       jsr _scr_init
+       jsr _init_channels
+
 ; Go directly to main(). No support for CLI arguments, no saving
 ; any machine state for a clean exit, because we don't exit.
        jmp _main
diff --git a/src/main.c b/src/main.c
index cfc9641..3b24182 100644
--- a/src/main.c
+++ b/src/main.c
@@ -132,8 +132,6 @@ void main(void) {
   bell_type = config.alert_type; /* TODO: have bell.s read staight from the struct */
 
   edbox_clear();
-  scr_init();
-  init_channels();
 
   while(1) {
 	  if(fn_connect()) {
-- 
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