Merge remote-tracking branch 'upstream/master'

[cc65] / libsrc / c64 / crt0.s

diff --git a/libsrc/c64/crt0.s b/libsrc/c64/crt0.s
index f75a5c46b1e11bb8337b9d6b01ae964c762a0f95..ab44e9033837cf805a71b3ebc3b742e9f563c34d 100644 (file)
--- a/libsrc/c64/crt0.s
+++ b/libsrc/c64/crt0.s
@@ -1,123 +1,111 @@
 ;
 ; Startup code for cc65 (C64 version)
-;
-; This must be the *first* file on the linker command line
 ;
 
-       .export         _exit
-       .import         initlib, donelib
-               .import         zerobss, push0
-       .import         callmain
+        .export         _exit
+        .export         __STARTUP__ : absolute = 1      ; Mark as startup
+        .import         initlib, donelib
+        .import         zerobss
+        .import         callmain
         .import         RESTOR, BSOUT, CLRCH
-       .import         __RAM_START__, __RAM_SIZE__     ; Linker generated
+        .import         __RAM_START__, __RAM_SIZE__     ; Linker generated
+        .import         __STACKSIZE__                   ; Linker generated
+        .importzp       ST
 
         .include        "zeropage.inc"
-       .include        "c64.inc"
+        .include        "c64.inc"
 
 
 ; ------------------------------------------------------------------------
-; Place the startup code in a special segment.
-
-.segment               "STARTUP"
+; Startup code
 
-; BASIC header with a SYS call
+.segment        "STARTUP"
 
-        .word   Head            ; Load address
-Head:   .word   @Next
-        .word   .version        ; Line number
-        .byte   $9E,"2061"      ; SYS 2061
-        .byte   $00             ; End of BASIC line
-@Next:  .word   0               ; BASIC end marker
-
-; ------------------------------------------------------------------------
-; Actual code
+Start:
 
-       ldx     #zpspace-1
-L1:    lda     sp,x
-       sta     zpsave,x        ; Save the zero page locations we need
-       dex
-               bpl     L1
+; Save the zero page locations we need
 
-; Close open files
-
-       jsr     CLRCH
+        ldx     #zpspace-1
+L1:     lda     sp,x
+        sta     zpsave,x
+        dex
+        bpl     L1
 
 ; Switch to second charset
 
-       lda     #14
-       jsr     BSOUT
+        lda     #14
+        jsr     BSOUT
 
 ; Switch off the BASIC ROM
 
-       lda     $01
-               pha                     ; Remember the value
-       and     #$F8
-               ora     #$06            ; Enable kernal+I/O, disable basic
-       sta     $01
+        lda     $01
+        pha                     ; Remember the value
+        and     #$F8
+        ora     #$06            ; Enable kernal+I/O, disable basic
+        sta     $01
 
 ; Clear the BSS data
 
-       jsr     zerobss
+        jsr     zerobss
 
 ; Save system settings and setup the stack
 
         pla
-        sta    mmusave         ; Save the memory configuration
+        sta     mmusave         ; Save the memory configuration
 
-               tsx
-               stx     spsave          ; Save the system stack ptr
+        tsx
+        stx     spsave          ; Save the system stack ptr
 
-       lda     #<(__RAM_START__ + __RAM_SIZE__)
-       sta     sp
-       lda     #>(__RAM_START__ + __RAM_SIZE__)
-               sta     sp+1            ; Set argument stack ptr
+        lda     #<(__RAM_START__ + __RAM_SIZE__ + __STACKSIZE__)
+        sta     sp
+        lda     #>(__RAM_START__ + __RAM_SIZE__ + __STACKSIZE__)
+        sta     sp+1            ; Set argument stack ptr
 
 ; Call module constructors
 
-       jsr     initlib
+        jsr     initlib
 
 ; Push arguments and call main
 
         jsr     callmain
 
-; Call module destructors. This is also the _exit entry.
+; Back from main (This is also the _exit entry). Run module destructors
 
-_exit:         pha                     ; Save the return code
-       jsr     donelib         ; Run module destructors
+_exit:  pha                     ; Save the return code on stack
+        jsr     donelib
 
 ; Copy back the zero page stuff
 
-               ldx     #zpspace-1
-L2:    lda     zpsave,x
-       sta     sp,x
-       dex
-               bpl     L2
+        ldx     #zpspace-1
+L2:     lda     zpsave,x
+        sta     sp,x
+        dex
+        bpl     L2
 
 ; Place the program return code into ST
 
-       pla
-       sta     ST
+        pla
+        sta     ST
 
 ; Restore system stuff
 
-       ldx     spsave
-       txs                     ; Restore stack pointer
-               ldx     mmusave
-       stx     $01             ; Restore memory configuration
-
-; Reset changed vectors, back to basic
+        ldx     spsave
+        txs                     ; Restore stack pointer
+        ldx     mmusave
+        stx     $01             ; Restore memory configuration
 
-       jmp     RESTOR
+; Back to basic
 
+        rts
 
 ; ------------------------------------------------------------------------
 ; Data
 
-.data
+.segment        "ZPSAVE"
 
-zpsave:        .res    zpspace
+zpsave: .res    zpspace
 
 .bss
 
-spsave:        .res    1
-mmusave:.res   1
+spsave: .res    1
+mmusave:.res    1